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If a rigid plate is bounded by two transform faults and the plate is moving, with the translatory motion of the plate will there be oscillatory motion as well? If not, why and if there is an oscillatory motion then what will be the mechanism of it?
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In my article on RG 'The driving forces of tectonic activity' I propose a mechanism that can explain an oscillatory motion of moving plates.
It is well documented that tectonic activity has a seasonal variation. The article gives a mechansm based on the axis tilt of the earth with a different velocity ( and centr@ifugal force) of the earth hemispheres in the rotation around the sun according to the seasons.
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Hi,
I am looking for recommendations of any open source geodynamic modelling software that could help me model how the style of subduction initiation impacts the geometry of the resulting slab?
By "style of subduction initiation", I mean spontaneous (e.g. mantle plume, passive margin or transform collapse) or induced (transference or polarity reversal). So theoretically, I want to input the characteristics of these styles and see the geometry of the slab produced.
Thanks,
Shane
Image from Stern and Gerya (2018)
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How about ASPECT(https://aspect.geodynamics.org/), which is supported by CIG (Computational Infrastructure for Geodynamics). It's easy to get started , but I haven't use ASPECT for subduction initiation. And I think you could have a brief look about it , I hope it's useful to you (https://github.com/geodynamics/aspect).
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How can we relate the abundance and composition of granitoids to the geodynamic context in which they formed?
Why the granitoids are abundant in the Hercynian belt in the Western Europe?
Why the granitoids are scarce in the Calcedonian and Alpine Orogenies?
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There is not a straightforward answer to your question. The abundance relates to the temperatures reached, the compositions of the source rocks (metaseds, metaigneous, mantle or a mixture of all three, and the amount of volatiles, particularly water. There are some general patterns that one may see in specific settings e.g., Pearse and others or Frost et al. (2001).
Arcs tend to have calcic magnesian compositions, becoming more ferroan as melts differentiate, generally I-type. Continental collisional granites tend to be more S and A-types.
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This topic has been open for a wide range of researchers here and outside of RG, as open access to write and read comments related.
I encourage researchers with a deterministic view on earthquake nature for being proactive by trying to use resources of this space as much as possible in a way of understanding this phenomena by challenging their forecast models through forecast tests.
On forecast, I would like to find the method, data and time window for forecast, with magnitude range and probability of occurence. If the location of future event is possible, please specify. It's a test, and additional option to write about our successful forecasts and our correct models.
Also, please be concise, as possible.
In addition, I suggest to make references to own research, or other sources, for keeping the transparency on sensitive questions such as autor rights, originality and other aspect. For this, in case of not published yet ideas, I suggest to publish and come down in the comments with reference to official open to public source - article.
N.B. Regarding the forecasts based on statistical methods, and random nature of the EQ phenomenon view, are also welcomed.
Sincerely,
Sandu I.
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Dear Sandu,
You have right, In the zone happened three earthquakes around 'M: 7.4' onto the base of Google map see the attached file.
Regards,
Laszlo
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Paleomagnetic studies show that the South China block was moving northward continuously from 300 to 260 Ma and has experienced an overall ∼27° clockwise rotation since then (Huang et al., 2018) ,and assuming a stationary Emeishan mantle plume, so if I want to do a numerical simulation of the geodynamics of the Emeishan mantle plume based on the above conditions. How can I do it?
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Hello dear;
I didn't research on Paleomagnetic studies, but i know 2 methods in order to behavioral study between two things. K-means clustering and Artificial Neural Network (ANN). you can read this combination method in this paper :
good luck
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Plate tectonics is a theory that states that plates on the Earth's surface move as rigid bodies. GPS is a system that is working independently on the theoretical motions of these theoretical plates, which means that the motions of plates must be visible when studied by passive GPS receivers (if you don't think so, tell us). Some studies work with the so called plate-fixed (net rotation) reference frames, such as e.g. NAD83, that use GPS data, but state that the frame is plate-fixed - no plate motion is visible. My question is: Is it possible that one creates a plate-fixed frame for GPS? If you think so, please, describe the process. I repeat that GPS does not care about the reason why the passive receiver changed its position - so how can you fix your data to a theoretical motion of a plate?
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I concur with Jan
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My question is about occurred geodynamic events related to alkaline magmatism between Ordovician-Silurian periods in Central Iran tectonomagmatic zone or near adjacent zones.
Furthermore, the effective geodynamic events within the Gondwana at 500-400 Ma is very important to sole my problems.
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I am looking for explanatory model for the of REE - Nb - U mineralisation in Siwana Ring Complex, Rajasthan, India with reference to its magmatic evolution, tectonic implication, and geodynamic history.
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Siwana Ring Complex (SRC) is most spectacular and spatially related Ring Complex of Neoproterozoic Malani Igneous Suite (MIS) . Basically, there are two accepted and Preferred model for the geodynamic system of MIS, one is plume related extensional model and another is subduction related model. The high concentration of REE-Nb-U in Siwana granitoids is due to crustal assimilation of Protolith melt that was generated through a mantle plume. The anorogenic character of rock-types of SRC ruled out any External fluid role in the enrichment of these incompatible elements. Therefore, to understand the magmatic evolution, tectonic affinity and geodynamic of SRC, the plume related extensional model should be very preferable.
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Hi, I would like to calculate the complereness magnitude from the earthquake catlog.
Does anyone know any programs or free software?
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What is a-annual in the FMD graph in ZMAP?
Can it be used to calculate the probability of exceedance of threshold magnitude?
I need to use Z map data in R-Crisis for PSHA analysis.
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Dear all, I'd like to open here a sort of forum for understanding how the geodesists community is moving in view of the X-band SAR satellite constellation. The new constellation will offer new "free, near real-time SAR data" with the "latest information about any spot on the planet within the hour". This will open completely new horizons for InSAR monitoring of ground deformation especially for rapid phenomena such as eruptions and seismic crises. The huge amount of so frequent data acquisitions will open also new needs for rapid and automatic processing. My question are: who knows more? Are you planning a routine use of these data? How?
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Wow, thank you. I'm looking for understanding their high-frequency repeated interferometry for ground deformation monitoring. Will data be open or should they be bought?
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I am interested in sesmic tomography data (such as pictures) of the Dzhungarian basin, Tarim and Eastern Kazakhstan. The purpose is to undestand the geodynamic and tetonic processes at the collision, subduction zones.
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Mr. Ernest Berkman, thank you for information. I will definitelly review mentioned articles.
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I am searching the web for "Thrustpack" modeling software but haven't come across it. Is it open access? Are there any alternative open-access codes for forward kinematic modeling of thrust belts?
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Hi There! You should try the Andino, one of the most powerful modeling softwares, and it is available in full for free academic use,
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Please tell me where oceanic crust is very thick and why? Is it related to the plume? I hope to listen a diffrent answer(one place which has thick oceanic crust, but the reason is uncertain)
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Yes it does. You can read more about crustal thickness beneath 900East ridge (Indian Ocean), Walvis ridge (Atlantic Ocean), Shatsky rise (Pacific Ocean) etc.
Oceanic crust under the influence of plumes may get thickened by magmatic addition at the base of the crust. Processes of such 'underplating' may depend upon prevailing tectonics. I suggest you read more about oceanic plateaus and aseismic ridges to discover more.
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Most crucial ground and borehole geophysical data are on the hands of oil and gas companies. They are not free for students, young researchers and for those who can not pay the quest or can not get access to data. In my opinion, these limits the effort of several researchers in their further work to understand the earth, its resources and estimating serval reservoir parameters.
  • How can we get open sources or low coast reliable geophysical data? I want to ask geophysicists and geoscientists, who are using available open sources or low cost reliable geophysical data. What do you recommend or suggest ?. Any recommended data may be useful for detail geological / reservoir interpretation, geodynamics studies or earth resources exploration at large scale, detailed and small scale, or even at laboratory scale. Can those data be processed and interpreted to be published in highly -ranked journals?
Kind regards
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Dear Mulugeta Chanie Fenta, nice to meet you.
There are a lot of programs to help the students and professors, I know by myself about that due that I was professor / teacher in Applied Geophysics as the same time I was (I still on activity) working in the E&P research and development for Oil and Gas industry (Exploration and Production), not only with the most advances technologies in 3D seismic tools, but also with the latest advances in 3D grav/mag modeling and inversion.
I can say you by my own experience, that there are a lot / several companies that try to help students, not only with datasets such as seismic or well-logs or geological data, but also with software’s and with programs of scholarship and training. It is a natural process to sign an agreement between the universities and the oil companies, under a confidentiality’s umbrella, it is a win-to-win scenario, particularly in the case of 3D seismic data that it is the hard data to get, and also because in case of seismic, you must - additionally - need the dataset from well-logs to work in the interpretation.
On the other hand, organizations such as AAPG; SEG; EAGE, AGU, in this COVID-19 pandemic’s time offer a lot of webinars and presentations / virtual events, free. If you chek the web, upcoming free online webinars, just you do have to be registered for the webinars and that´s all!!!
Visit please for example:
Please, let me know if my answer satisfied your expectations, I try to help you.
Best wishes, Mario E. Sigismondi
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I have got the first-hand paleocurrent data in the field by measuring the oriented
pepples and crossing beds. And now, except making the stratigraphic rotation,
what else should I do next ? Should I consider the roation of the block according
to the paleomagnetic data? and what I should do if none?
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read Roy Lindholm book to know about tilt correction in paleocurrent database
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Is there any relation between the shape of the elliptical earth and the prediction of the epicenter of earthquakes?
There are many causes of earthquakes. Tectonics plates and geodynamic conditions control the earthquake occurrence in active regions. Thus monitoring the subsurface conditions clearly help us to predict an earthquake epicenter. It is well known that the energy explodes in weak regions, fractured area or the most easiest break up part of earth.
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Earthquake or what I sometimes call geo-quake builds up becuse of stored energy that is lurking within the subsurface. The position of the epicenter, earth's surface above the focus of an earthquake where this energy lurks does not depend on the shape of the earth nether can the shape of the earth be used to predict, but it relates to the mobile plates, which create disequillibrium above, below and around the position of the lurking energy. The resuling disequilibrium causes the sudden release of energy, which is disastrous whenever it occurs. Its prediction can be achieved by assessing the seismogenic activities few hours before and few hours after the earthquake/geo-quake.
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To my knowledge, during this Archean, the crust experienced a marked change in composition from sodic TTG assemblages to medium- and high-potassium calc-alkaline granite-granodiorite suites and sanukitoids . The specific timing of this change varies from craton to craton and is accompanied by significant changes in geodynamic settings associated with crustal thickening and reworking that contributed to the final stabilization of the cratons.
I have some samples that synchronous TTG gneisses and potassic granitoids in the given region? anybody know studies about this ?Many thanks in advance for sending me messages about this.
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this paper is a good place to start:
Martin, H., Smithies, R. H., Rapp, R., Moyen, J. F., & Champion, D. (2005). An overview of adakite, tonalite–trondhjemite–granodiorite (TTG), and sanukitoid: relationships and some implications for crustal evolution. Lithos, 79(1-2), 1-24.
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Esteemed Academicians,
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SUNJAY
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Dear Sunjay2: Usually geologists and other earth scientists make very concrete questions in this page, but you make none, so what is there to answer?
Regards, Sebastian
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Any one please give some comments on the problem given below:
In Geosoft Oasis Montaj ,while calculating the radial power spectrum in MAGMAP,the power spectrum is radially averaged, as a result if larger grid is available , the smoother the  power spectrum will be.
The file scripted in Geosoft Oasis montaj contains 5 fields - the wave number increament, no. of samples averaged, the logarithmic of averaged wave no. and a 3 and 5 point depth estimate provides the result automatically(PDF 2-ENERGY SPECTRUM).
While dealing with real field data, ln (power) vs wavenumber K and depth estimate vs wave number K  problem occurs with their data values and   units in given fig 1 (POWER SPECTRUM),please  give some interpretary comments? is it problem with the data collected? 
Is there any other way which is reliable for calculating depth estimate of potential field data using Power Spectrum?
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I attached my own research about your question dear colleagues.
Cheers, Mario E. Sigismondi
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Please, i'm looking for a copy of a Book : "Principles of Alluvial Fan Morphology ( Dan Bowman )", can you help me to find it ??
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Your email
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Linear magnetic anomalies are observed in the seafloor spreading. If we are having 10 transects in an ocean basin then for a particular magnetic Chron, amplitude of magnetic anomalies (normal or reverse) along all the profiles can vary (due to the thickness of oceanic crust). But how much magnetic anomaly variation, we can expect, for a particular magnetic Chron in all the transects.
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Pankaj, if you send to me a map with the coordinates, I can try your ZOI with WDMAM.
Whenever you want, Mario
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i have been trying to install the Gamit/Globk but cant find the exact installer file. i have been reading the "intro to GG" but still can't find my way around linux
maybe an idea would help
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Hi,
I recently have made these tutorial videos on youtube...how install and test gamit-globk...hope will help you...
cheers,
A. Fadil
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I am presently working on local geoid model determination using gravimetric-geometric method. To obtain the gravity anomalies of chosen points, the points absolute gravity and their respective theoretical gravity must be obtained. Someone should please help me, I want to know if it is ideal to compute the theoretical/latitude gravity on WGS84 ellipsoid or it must be computed on the local ellipsoid adopted for geodetic computation in the area of study.
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If you need to determine WGS 84 geoid then you shall compute the standard gravity (Latitude) on WGS84, otherwise for local geoids you have to use your local ellipsoid parameters
Wish you all the success
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Dear all
I'm going to process an embankment dam with geostudio SIGMA/W module. want to know how can I consider the effect of time in my processing? In other words, 10 or 15 years after dam construction has finished, how to predict the behavior of dam such as displacement in X or Y directions, total stress and so on?
All the best
Emad
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Dr. Lotfollah Emadali,
In Sigma/w, you can check "Coupled Stress/PWP" or "Volume Change" analysis. However, the problem here is your period of consideration (15 years), it is too long. You can convert your hydraulic conductivity into m/day, and choose the time steps to be "a week or half a month (as small as possible).... , increase the Number of Iterations, ...Just check the outcome if it is ok?
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Dear all,
I am looking for papers that show crustal extension estimates during the formation of a conjugate pair of continental rifted margins (I am happy with any pair of rifted margins).
Please, could you point me out towards literature about this?
Many thanks,
Júlia
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Hi, from my point of view, and some might have mentioned this already in the discussion, continental breakup is not the separation of the crust, but the entire continental lithosphere. This can get complicated and depends on inheritance, magmatism, extension rate and thermal state of the lithosphere. In Petersen & Schiffer (2016) we have explored and discussed this. You can find also a number of relevant references. When your crust/lith is warm, you can create highly thinned (hyperextended) margins, before breakup. Vice versa, a cold crust/lith. will "snap" and create abrupt, only minorly thinned margins. It's the interplay of crustal vs. mantle rheology, leading to depth dependent extension. cheers, Christian
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I have information about temperature, pressure, normal and shear stresses, viscosity, conductivity, density, heat capacity and adiabatic heating for a particular area of mantle in the form of 2D matrices. I want to show phase relation for this region of mantle. Is there an equation (group of equations) which relates phase relation for mantle with these properties?
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My name is Boris Kapochkin. I wrote several monographs on the geodynamics of hydrogeology and the forecast of earthquakes. I consider it important to study the landslide process called slow earthquakes and changes in groundwater level. I have determined that hydrogeology can be the cause of rainfall and not vice versa. I understand that this information is known to you.
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Ok.
The anticyclonic type of weather is high atmospheric pressure.
  The level of groundwater depends very much on geo-information. Much more than from other factors.
Borys.
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Perhaps this question does not leave many Geologists and Geophysicists perplexed that Plate Tectonics is the engine of change, but the existence of passive and active margins as we know today, it has not always been the same.
This question is somewhat disconcerting for the Geophysicists even today. The best theories offer a range of possibilities: lateral buoyancy contrast (Niu et al, 2003); the role of water (van der Lee et al., 2008); ductile deformation of passive margins (Goren et al., 2008); geodynamic forces such as rifting and plume ascent (Burov and Cloetingh, 2010); higher Moho temperature (Nikolaeva et al., 2011) from numerical models.
Today, there are two mechanisms recognized: induced and spontaneous.
Do you have some article or research to share?
Best wishes, Mario E. Sigismondi
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Dear Mario, Before determining the origin of any phenomenon, it is good to understand what kind of phenomenon it is. In the case of subduction, everything is complicated due to the fact that it has been tied for a very long time to the unconfirmed idea of ​​the infinite sinking of the oceanic crust, which constantly draws down the descending movement of the mantle convective cell. If we look at "subduction" soberly, we can say that it is most likely a zone of interaction between oceanic and continental slabs with predominant compression, an analog of a collision, or obduction, but with a predominant under-thrust component. Now in the zones of "subduction" compression and underlay predominate, later in the framework of the oscillatory process they can be replaced by stretching and spreading. Infinite podviganie plates on the outer part of the descending convection cell is unlikely by the elementary laws of physics. The geometric impossibility of this is proved among other authors and by me. Below is a reference of my abstracts on EGU-13 and mu presentation on EGU-14 on this topic.
Geophysical Research Abstracts
Vol. 15, EGU2013-6448, 2013
EGU General Assembly 2013
© Author(s) 2013. CC Attribution 3.0 License.
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Some researchers (Sablukov; Buslovich) predict that there are mezosoic kimberlites on East European Craton (EEC). Is there any evidence?
The only reason is the presence of KIM's in mezosoic sediments of the north-eastern part of Mezen syneclise (northern part of EEC). It looks unreliable to me because Devonian kimberlites are located on the north of Mezen syneclise.
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Unfortunately, all these publications are on Russian.
A. Buslovich "Мезозойские трубки взрыва Вологодской области" (Mesozoic explosive pipes of Vologodskaya oblast')
Also, there is another author V. Tret'yachenko "Перспективы мезозойского кимберлитового вулканизма юго-восточной части Архангельской алмазоносной провинции" (Perspectives of mesozoic kimberlite magmatism of the southeastern part of Arkhangel'sk diamond province)
Here is a link on the latest Sablukov's presentation (June 2017) about "highly perspective" Ust'yanskaya area where he propose mesozoic kimberlites:
Regards Alexander
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A-type granitoids are important geodynamic markers. It is therefore crucial to know the age of the oldest A-type granitoids (both A1 and A2 type) of the World.
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If was aware about. It seems that you have enough knowledge, Your polite comportment its reflect well...
I think we do not know to give such a response: which you do not aware it.
If you practice an examination procedure, its better to do with your students
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Please suggest me how to calculate stress accumulation and strain using gps displacements for understanding the occurrence of failure (earthquakes).....
Thank you
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The simple answer to get to strain from displacements is to find the deformation matrix that connects initial to final positions. If you are working in 3D that would be a 3D tensor. If you could assume plane strain the matrix would be simpler. Basically the displacements would be longitudinal and angular and you could go about quantifying those depending on your problem. If your data consist of GPS displacements, it is the longitudinal strain (typically N and E) that is significant and you can look at "baselines" that shorten or extend in the direction that is most important to you. As Stress and Strain tensors are connected through the Rheology tensor, you would need to have information about the rheology of the deforming material to be able to go from strain to stress (as Martijn correctly pointed out above). If the deformation is near surface then elastico-frictional laws typically apply. Other wise you could opt for quasi-plastic or viscoelastic rheologies.
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Is Geodynamics have any direct or indirect relation with Ecology, preferably Agriculture? or Geodynamics have any direct or indirect impact on Agriculture? if so, what?
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Yes Geodynamics have indirect relation with agroecology or rather say cultivation of crops. The any dynamism on soil either on surface or inner layers bound to impact by changes which ultimately link to rhizopspheric interaction in crops.
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Hello every one,
Can you help me out, what are the major factors that influence the plate velocity?
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A specific plate velocity, described by an Euler vector, results from an equilibrium equation between active and passive torques exerted on a tectonic plate. An example of this equation can be found in:
Schettino, A. & Macchiavelli, C., 2016. Plate kinematics of the central Atlantic during the Oligocene and Early Miocene, Geophysical Journal International, 205, 395–413, DOI: 10.1093/gji/ggw022.
Passive torques arise from passive asthenosphere drag. Active torques are associated with 1. active asthenosphere drag when lateral changes of pressure occur in the upper mantle, 2. lateral changes in the age of the lithosphere, which generates the so-called ridge push, 3. slab pull when the tectonic plate is subducting beneath another plate.
You could also give a look at chapter 13 of my book Quantitative Plate Tectonics.
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Fundamentally, we can address the key initial parameters in planetary formation, dynamics, and evolution as being astrophysical in nature. These astrophysical parameters lead to specific geologic and atmospheric conditions of every planet or moon. In a search for the most fundamental quantities that determine the characteristics of a planetary surface and atmosphere, I have devised the attached categories and list of parameters. My question is, which of these are the most fundamental and influential to the evolution of a planet or moon? Has the magnitude of importance of these fundamental quantities been tested? Most importantly: what mostly dictates how a planet become its unique set of conditions? Some qualities are guaranteed to be more imprint in some scenarios than in others, but which are the most common, and how do they manifest together into a unique planetary body? For example: changes in what parameters lead to what different planetary outcomes?
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The most fundamental property is likely to be the composition of the nebula the planetary system and star formed from. The ratios and abundances of certain elements from the nebula they all formed from will dictate the end composition of all the planets and the star itself.  All other variables are going to be influenced by the initial composition.
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Hello everybody, 
I am looking for a reference paper which exploit the factor of anisotropy which obtained by applying a geoelectrical survey over an area. The factor of anisotropy (lambda) is usually calculated from Dar-Zarrouk Parameters ( the transverse resistivity and longitudinal resistivity). What iam looking for is a research paper dealing with a direct useful application for lambda 2D maps in detecting subsurface heterogeneity for a specific objectives. 
Regards. 
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Semail ophiolite in Oman obducted on southeastern margin of Arabian plate is more or less at the boundary between the Arabian, Eurasian and Indian plate. I want to know if the obduction and post obduction history of ophiolite can be related to regional tectonic frame work of this region. whether the obduction itself is resulted by tectonic uplift, exhumation of Zagros orogeny? or what else? ideas and data? suggestions?
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Munazzam Hello
Your question is not simple. At the same time, I propose that our paper (you can find it in RG DataBase) will be useful for you:
Eppelbaum, L.V. and Katz, Yu.I., 2016. Tectono-Geophysical Zonation of the Near and Middle East and Eastern Africa. International Journal of Geology, 10, 1-10.
Best
Lev
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Yes this is a bit broader question but I want to know which processes play their role in movement of magma. If one wants to model magma intrusion in rocks, which processes should one not miss at all and which equations discuss these processes?. As a starter I can that we can use Navier Stokes equations for velocity fields, continuity equation for pressure distribution etc.
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I recommend reviewing the equations of the following topics:
a) A spherical expansion source at depth can simulate the change in storage of a magma chamber and account for deformation caused by magma intrusion events [Mogi, 1958].
b) Finite Element Models
c) Inverse analyses
d) 3-D visco-elasto-plastic numerical models of rock intrusion emplacement incorporating in particular the temperature-sensitive properties of both magma and country rocks. Thermomechanical modelling of magma intrusion involves simultaneous and intense deformation of materials with very contrasting rheological properties:
1.- the country
2.- crustal rocks
3.- visco-elasto-plastic while the intruding magma is a low viscosity
4.-complex fluid
Reference: Burg, J.P. & Gerya, T.V. (2008)
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We would like to pick zircons from a fine-grained sedimentary rock which has much amount of pyrite. Without any chemical treatment, we want to get rid of pyrite. I checked their densities and magnetic susceptibilities, but they are not so different. What do you recommend me? Are there some heavy liquids or other physical process to seperate pyrite?   
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 Dear Zehra,
I understand that the separation of minerals is not the most important of your business.
The simplest method of separation - manual separation of minerals during irradiation with UV radiation. Zircon will luminesce green-yellow light color (see answers to Petra Vesela). Pyrite is not luminescent.
If you have a lot of minerals, I recommend using the automatic X-ray luminescent separators, which are used for diamond industry. In the diamond industry zircon is a poor mineral which is extracted together with diamond and clogs concentrate.
But if you do not afraid some change the characteristics of zircon, it is possible to heat a mixture of pyrite + zircon at 200 -300C for 10 - 15 minutes. After that, zircon becomes lighter, but they restore color later. The pyrite becomes magnetic. After the procedures ferropirite is removed by magnetic fild.
Vasily
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The continental drift is a reality now, supported by the dynamics of plate tectonics and seafloor spreading. Continuous convergence (collision) and divergence (separation) of continental and oceanic plates from each other has been reshaping our Earth since the initiation of the process. Therefore, the absolute location (latitudinal and longitudinal) of places has been changing with the change of associated biotic and abiotic environments (tropics shift to equator, or polar regions being shifted to mid latitudes for example). 
Then, how the shape of the earth arises due to the continuous movement of the continents and oceans is impacting the global climate? Does it also impact the paleoclimatic records which are being considered to understand the climate of the past?
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Dear Sumanta: the question you posed is a very complex one! The supercontinent cycle has been operating since at least the Paleoproterozoic or Neoarchean, assembling and disrupting continental masses, creating -and destroying- orogenic belts and ocean basins, volcanic belts, and the like. So it is unquestionable that such tectonic variarions had a strong influence on past climate, just as they have been doing since the Pangea disruption in the Jurassic. The problem is relatively easy to resolve in Mesozoic terrains, a bit more difficult in Paleozoic, and really a hard one in the Precambrian. Conditions for deposition of evaporitic basins were widespread during the Permian, but also in the Devonian and Proterozoic, where large evaporitic basins are found, also aeolian sandstones are frequent in this very dry period, and in older times too. Climate changes so profound as to be unimaginable to us happened when continental blocks collided to form supercontinents. Pangea was covered possibly by a desert three times larger that the actual Sahara, and by an enormous ice cover in its southern parts. The uplift of the Appalachian-Caledonian belt surely had a profound effect in the climate of this supercontinent and global Earth. Before this, in the Neoproterozoic, the uplift of the world-wide Greenvillian system of orogenic belts, which was probably even higher than the Himalaya and longer than the Andes..., due to the assembly of Rodinia, certainly had a marked influence in atmospheric and oceanic circulation, as to eventually lead he planet to the "Snow-ball Earth" global glaciation, just as the uplift of the Andes and Himalaya has done in more recent times, creating large deserts in South America and Central Asia. The problem in older terrains is the large uncertainties in the relative shape, positions and paleolatitudes adquired by land masses, this is relatively easy to solve during the Jurassic, but increasingly difficult to ascertain in older times. With regards, Sebastian.
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Hello ,
I am looking for standard curves specialized for faults detection by using the (HEP) Horizontal Electrical Profiling technique in a ground resistivity survey.  Please inform with a reference or file related to this technique. 
Best Regards. 
Dr.  Wadhah M.  Shakir
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There are no standard curves dedicated or specialized for faults detection using HEP in ground resistivity survey. The HEP could only detect fractures which are usually characterised by relatively low resistivity. However, you can obtain a large data set of HEP and carry out deep vertical electrical soundings (VES) at the delineated fracture points using current electrodes spacing ranging from 2 metres to greater than 300 metres and construct geoelectric sections along the appropriate traverses. This would reveal network of fractures and possibly faults could be delineated if present.
Good luck.
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Sanukitoids are granitoids showing enrichment of both large-ion lithophile elements (K, Ba, Sr) and mafic elements (Mg, Cr and Ni) at the level of their SiO2 contents. It is generally thought that these granitoids, with high Mg#, were produced from a mantle source (supplying Mg, Cr and Ni) fluxed with a crust-derived fluid or melt carrying K, Ba, Sr, LREE and Th. A likely tectonic setting is a mantle wedge overlying a subducted oceanic slab undergoing dehydration or melting. Therefore, many authors consider presence of sanukitoids as a strong indicator of subduction, especially in the late Archaean. Can such rocks form in tectonic settings unrelated to subduction?   
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I believe you can find a detailed answer to your question is in chapter 3 of our book: Mints et al. "East European Craton: Early Precambrian History and 3D Models of Deep Crustal Structure" GSA Special Paper 510, 2015. You may copy Chapter 3 from ResearchGate.
In page 111 you can read:
Nature of sanukitoid magmas. As was shown above, the model Nd ages of sanukitoids definitely depend on the age of country TTG gneisses, which reflects either the age of the crust and the lithospheric mantle. Sanukitoids in the young Kuhmo–Segozero microcontinent have Nd isotopic parameters of the depleted mantle, whereas sanukitoids from the older Vodlozero and Kianta microcontinents are characterized by lowered initial εNd values. In the opinion of Kovalenko et al. [2005], the isotopic heterogeneity of sanukitoids is a result of different duration of a gap between enrichment of the mantle source and the moment of partial melting of that source, which produced sanukitoid magma. The two-stage model of the formation of sanukitoid magmas is a natural consequence of this statement. The first stage corresponds to the mantle metasomatism, i.e., enrichment of the mantle under effect of fluids or melts generated in the process of subduction or underplating of the crust by mantle-derived magmas. The second stage, which started 2.76–2.70 Ga ago, corresponds to the tectonothermal event (vigorous influx of extracrustal heat), which gave rise to the partial melting of the previously metasomatized mantle and generation of sanukitoid magma.
It should be noted, however, that a gap between formation of the crust (with or without participation of subduction) and formation of sanukitoids is cardinally different for three microcontinents making up the Karelian Craton. For the Kuhmo–Segozero microcontinent, this gap does not exceed 60 Ma. For the Kianta microcontinent, the gap is estimated at 60–100 Ma. Finally, for the ancient Vodlozero microcontinent, a gap could have been more than 150 Ma. These estimates convincingly show the absence of genetically predetermined succession of events: subduction → formation of continental crust of granite–greenstone domain → sanukitoid magmatism that completes formation of this domain. Following Kovalenko et al. [2005], Lobach–Zhuchenko et al. [2005b], and Bibikova et al. [2005b], we assume that the two-stage model is consistent with available geological and isotopic data, which reflect tectonic and geodynamic independence of the consecutive stages in the formation of sanukitoid magma. The crucial factor that initiated appearance of sanukitoids irrespective of prehistory of the crust is a thermal pulse dated at 2.76–2.70 Ga.
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Any suggestions on how to measure the thickness of the interlayer between the "brucite-like" layers in hydrotalcite minerals? Are these types of measurements being made, or do we need to do calculations? I have a rough idea of the spacing, as carbonate ions and water fit in, but could the spacing be more? I need to figure out what can fit in there, and maybe chemical engineers can help (I am a geologist)?
Thanks in advance!
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The standard way of measuring interlayer thickness for sheet silicates of all types is by x-ray diffraction. The basal reflections are usually strong enough even when the grains are oriented randomly with respect to the x-ray beam (place s few drops of slurry onto a glass slide and let it dry, then place into the diffractometer). Strongest basal reflections- those that indicate the interlayer spacing- are obtained by disaggregating the material, putting into a beaker of water, letting the coarsest grains settle out for a few minutes, and taking a sample of the suspended fines (less than 10 micron particle diameter is ideal) using a glass tube. Carefully apply the suspension onto the surface of a clean glass slide, letting the surface tension hold the liquid into a mound, without spillage over the sides of the slide. Let it dry. Apply another layer or two, drying between applications of the slurry. Mount in the diffractometer and your basal reflections (interlayer spacings) will be strong because most of the particles will be laying flat on the substrate.
There are plenty of people doing x-ray diffraction analysis; most large universities would be equipped. This is a standard mineralogical technique, and you will need a technician who knows how to read and measure the diffractogram for its information on interlayer spacing.
But why go through all this? There is plenty of information in the mineralogical literature about the interlayer spacing of layer silicates such as brucite. And there are established techniques of soil chemical analysis that allow you to measure the cation-exchange capacity (CEC)of your material with respect to solute species such as Na, Ca, K, etc. if there is some particular species of exchangeable cation you're concerned about. I haven't looked into it, but I don't think the CEC of talc/brucite minerals is very high- in other words, these minerals don't exchange cations readily (not like smectite and other expandable clays).
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Hello everybody. I am interested on studies about the use of GPS/GNSS stations on geodynamics. Someone could sugest me some bibliography? Thanks in advance!
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Agarval M, Singh R, Meshram MK (2013) Linearly polarized planar inverted F-antenna for Global Positioning System and woldwide interoperability for microwave access applications. IET Microw. Anten. Propag. 7(12): 991-998
Ahn J, Kim S, Byun J, Kim AS, Kim Y (2013) Compact PCB-embedded GPS antennas loaded with a coupling strip and lumped elements for mobile phones. Microw. Opt. Technol. Lett. 55(2): 363-366
Akala AO, Rabiu AB, Somoye EO, Oyeyemi EO, Adeloye AB (2013) The response of African equatorial GPS-TEC to intense geomagnetic storms during the ascending phase of solar cycle 24. J. Atmos. Solar-Terr. Phys. 98: 50-62
Akala AO et al. (2013) Comparison of equatorial GPS-TEC observations over an African station and American station during the minimum and ascending phases of solar cycle 24. Ann. Geophysicae 31(11): 2085-2096
Aktuğ B, Yildirim O (2013) Regularized estimation of Euler pole parameters. Earth Planets and Space 65(7): 699-705
Aktuğ B et al. (2013) GPS constraints on the deformation of Azerbaijan and sorrounding regions. J. Geodynamics 67(SI): 40-45
Aktuğ B et al. (2013) Deformation of Central Anatolia: GPS implications. J. Geodynamics 67(SI): 78-96
Alam N, Kealy A, Dempster AG (2013) Cooperative inertial navigation for GNSS-challenged vehicular environments. IEEE Trans. Intell. Transp. Syst.14(3): 1370-1379
Alba D, Fairley P (2013) Interplanetary GPS comes a step closer. IEEE Spectrum 50(7): 11-13
Alem LN, Passini HF, Minutta RA (2013) Embedded system for the command of a high-gain antenna pedestal with GPS coordinates. IEEE Latin Am. Trans. 11(1): 190-195
Alfonsi L et al. (2013) Comparative analysis of spread-F signature and GPS scintillation occurrences at Tucumán, Argentina. J. Geophys. Res.-Space Phys 118(7): 44483-4502
Al-Shaery A, Zhang S, Rizos C (2013) An enhanced calibration method of GLONASS inter-channel bias for GNSS RTK. GPS Solutions 17(2): 165-173
Amerian Y, Hossainali MM, Voooghi B (2013) Regional improvement of IRI extracted ionospheric electron density by compactly supported base functions using GPS observations. J. Atmos. Solar-Terr. Phys. 92: 23-30
Amerian Y, Voosoghi B, Hossainali MM (2013) Regional ionosphere modeling in support of IRI and wavelet using GPS. Acta Geophys. 61(5): 1246-1261
Amiri-Simkooei AR (2013) On the nature of GPS draconitic year periodic pattern in multivariate position time series. J. Geophys. Res.-Solid Earth118(5): 2500-2511
Amiri-Simkooei AR, Zangeneh-Nejad F, Asgar J (2013) Least-squares variance component estimation applied to GPS geometry-based observation model. J. Surv. Eng. 139(4): 176-187
Anquela AB, Martin A, Berné JL, Padin J (2013) positioning. J. Surv. Eng. 139(1): 47-58
Ao CO, Haij AJ (2013) Monitoring the width of the tropical belt with GPS radio occultation nmeasurements. Geophys. Res. Lett. 40(23): 6236-6241
Aoyama Y, Doi K, Shibuya K, Ohta H, Tsuwa I (2013) Near real-time monitoring of flow velocity and direction in the floating ice tongue of the Shirase Glacier using low-cost GPS buoys. Earth Planets and Space 65(2): 103-108
Aranzulla M, Cannavo F, Scollo S, Puglisi G, Imme G (2013) Volcanic ash detection by GPS signal. GPS Solutions 17(4): 485-497
Ardaens JS, D'Amico S, Cropp A (2013) GPS-based relative navigation for the Proba-3 formation flying mission. Acta Astronautica. 91: 341-355
Astafyeva E, Rolland L, Lognonne P, Khelfi K, Yahagi T (2013) Parameters of seismic source as deduced from 1Hz ionospheric GPS data: Case study of the 2011 Tohoku-oki event. J. Geophys. Res.-Space Phys 118(9): 5942-5950
Bachman W, Oliveira M, Xu J, Sabina E (2013) Household-level global positioning system travel data to measure regional traffic congestion. Transp. Res. Record 2308: 10-16
Bakula M (2013) Study of reliable rapid and ultrarapid static GNSS surveying for determination of the coordinates of control points in obstructed conditions. J. Surv. Eng. 139(4): 188-193
Banville S, Langley RB (2013) Mitigating the impact of ionospheric cycle slips in GNSS observations. J. Geod. 87(2): 179-193
Basha G, Ratman MV, Manjula G, Sekhar AVC (2013) Anomalous propagation conditions observed over a tropical station using high-resolution GPS radiosonde observations. Radio Sci. 48(1): 42-49
Bevis M, Brown A, Kendrick E (2013) Devising stable geometrical reference frames for use in geodetic studies of vertical crustal motion. J. Geod.87(4): 311-321
Bhuyan PK, Hazarika R (2013) GPS TEC near the crest of the EIA at 95 degrees E during the ascending half of solar cycle 24 and comparison with IRS simulations. Adv. Space Res. 52(7): 1247-1260
Bidaine B, Lonchay M, Warnant R (2013) Galileo single frequency ionospheric correction: performance in terms of position. GPS Solutions 17(1): 63-73
Bierlaire M, Chen JM, Newman J (2013) Aprbabilistic map matching method for smartphone GPS data. Transp. Res. (Part C) 26: 78-98
Blewitt G, Kreemer C, Hammond WC, Goldfarb JM (2013) Terrestrial reference frame NA 12 for crustal deformation studies in North America. J. Geodyn. 72: 11-24
Blondi R, Ho SP, Randel W, Syndergaard S, Neubert T (2013) Tropical cyclone cloud-top height and vertical temperature structure detection using GPS radio occultation measurements. J. Geophys. Res.-Atmospheres 118(11): 5247-5259
Bonafoni S et al. (2013) Assessment of water vapor retrievals from GPS receiver netwok. GPS Solution 17(4): 475-484-1322
Bonforte A, Guglielmino F, Puglisi G (2013) Interaction between magma intrusion and flank dynamics at Mt. Etna in 2008, imaged by integrated dense GPS and DInSAR data. Geochem. Geophys. Geosyst. 14(8): 2818-2835
Bonnefond P, Exertier P, Laurain O, Thibaut P, Mercier F (2013) GPS-based sea level measurements to help the characterization of land contamination in coastal areas. Adv. Space Res. 51(8): 1383-1399
Boroujeni BY, Frey HC, Sandhu GS (2013) Road grade measurement using in-vehicle, stand-alone GPS with barometric altimeter. J. Transp. Eng.139(6): 605-611
Bos MS, Fernandes RMS, Williams SDP, Bastos L (2013) Fast error anaysis of continuous GNSS observations with missing data. J. Geod. 87(4): 351-360
Botteron C et al. (2013) Soil moisture & snow properties determination with GNSS in Alpine environments: Challenges, status, and perspectives.Remote Sens. 5(7): 3516-3543
Boutiouta S, Lahcene A (2013) Preliminary study of GNSS meteorology techniques in Algeria. Int. J. Remote Sens. 34(14): 5105-5118
Bowling T, Calais E, Haase JS (2013) Detection and modelling of the ionospheric perturbation caused by a space shoutle launch using a network of ground-based Global Positioning System stations. Geophys. J. Int. 192(3): 1324-1331
Branzanti M, Colosimo G, Crespi M, Mazzoni A (2013) GPS near-real-time coseismic displacements for the Great Tohoku-Oki earthquake. IEEE Geosci. Remote Sens. Lett. 10(2): 372-376
Brenot H et al. (2013) Preliminary signs of the initiation of deep convection by GNSS. Atmos. Chem. Phys. 13(11): 5425-5449
Cahyadi MN, Heki K (2013) Ionospheric disturbances of the 2007 Bengkulu and the 2005 Nias earthquakes, Sumatra, observed with a regional GPS network. J. Geophys. Res.-Space Phys 118(4): 1777-1787
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I have a segmented CT image of a pore geometry. I can compute the skeleton on the geometry no problem and get an estimated hydraulic radius at each location along the skeleton by interpolating the Euclidean distance transform. This method gives the distance between the pore centerline and the closest pore edge, essentially a measure of the radius of the inscribed sphere within a pore geometry. This is adequate for semi-cylindrical pores, but for irregular pores, the effective hydraulic radius is larger.
Is there a modified distance map transform that gives a better estimate of the effective hydraulic radius of a pore from a CT image?
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If you have a segmentation of the pores you can use connected component labeling (http://www.mathworks.com/help/images/ref/bwconncomp.html) and regioprops (http://www.mathworks.com/help/images/ref/regionprops.html) and than for each pore you can find the 'Orientation' property of the pore which is the best ellipse that is fitted to the connected component. 
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Any suggestion for geochemical discrimination diagrams for granitoids of various tectonic settings?
Chusi Li et al., 2015, ("Trace element indiscrimination diagrams"-Lithos 232) showed that many of the geochemical discrimination diagrams based on incompatible trace elements are not useful in distuishing basalts from various tectonic environments. With this in mind, I guess the distinction between granitoids  of different tectonic settings would be even more tricky. Any suggestions regarding some useful discriminants for granitoids?
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Dear Dr. Jan:
Let me add a general statement. I also was fond of using discrimination diagrams like those mentioned in this Q&A relation. It makes you think you have an ideal and efficient tool passing a lot of samples through an analytical device which does not only  provide us with read-outs of chemical data but delivers straight ahead the geodynamic setting in a way which can be satirized as "Mountain building out of the test tube". We are creating a plethora of results which having a closer look at the geology as it is in the field are in no way related to the real geology. Geoscientific work takes time and needs substituting the swivel chair for the campstool, at least from time to time. For those who are riding only the paper tiger it may be sufficient but those who also want to deal with earth in an extractive way or want to know more about only the interplay of mineralogical and chemical in-house studies with field work will provide us with lasting results.
Sorry for this comment. But from time to time I feel it is necessary to put in order the system and champion the cause of this unprivileged discipline "field geology", which cannot be underrated.
With kind regards
Harald G. Dill
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What is the most convinscing theory that discusses the generation of Earths magnetic field?
 Many  Geophysical references referred to magmatic currents which are rich in iron content  and located at the lower mantle and outer core composes the main source of magnetic field.  Iwould like to know if there are any new theories or any other references that discuss this subject.
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Your welcome.
There are many things that are unknown. But the temperature in the outer core is not a big deal. The Earth is not a magnet, the Earth is an electromagnet, is the circulation of electrons in the outer core which produced the magnetic field and not a remanence in the core.
Regards
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Respect Sir/Madam
I saw some of research articles reported micro-seismicity using linear array with close inter-station space. Also these studies reported more error in depth. How can we reduce this error. Is there any method for this type of work and can we apply that method for linear array with more inter-station spacing (~20-30 km).
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Dear Nagarayu, there is no special method of locating earthquakes with linear arrays, any localization program will work. A linear array, however, will always produce large localization errors for events lateral from the line, simply caused by the small differences of the arrival times. Why don't you shift 1 station  to get an areal array.
Kind regards
Rainer
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This microfabric is observed in a chrnockite (igneous origin) and here shown as a BSE photog. The slight gray crystals are oxpyroxenes while the black gray ones are felsic minerals. Anybody konw what implications this fabric has in relation to petrogenesis and how it growed?I have appended the BSE photo below. 
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Such texture occur in "eutectoids". I would call it symplectite in preference to myrmekite, The orthopyroxene and feldspar may have grown simultaneously.
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Hi to all!
I have some difficulties to find this:
Deibis, S., Futyan, A.R.I., Ince, D.M., Morley, R.J., Seymour,
W.P. and Thompson, S., 1986. The stratigraphic framework
of the Nile Delta and its implications with respect to the
regions hydrocarbon potential. Proc. 8th Explor. Conf.,
EGPC Cairo
Can anyone help me?
Thank you! 
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Dear All
I will try yo locate and make a pdf of this paper, but it will take a couple of weeks as I am travelling at the moment. Incidentally, I wrote and presented this paper, not apparent from the author list !!
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Is it possible to integrate online conversion from ellipsoidal heights to orthometric heights using, for example, GRACE gravity data and other prior knowledge?
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If you want to convert ellipsoidal heights to orthometric you can use the PROJ libraries with the geoidgrids for height conversion.  In python you'll need to get pyproj
<code snippet>
WGS84=pyproj.Proj(init="EPSG:4326") #WGS84 datum ellipsoid height
UTM19S=pyproj.Proj(init="EPSG:32719", geoidgrids='egm08_25.gtx') #Chile UTM coords, zone 19S, orthometric heights(masl)
 east, north, masl = pyproj.transform(WGS84,UTM19S, data.LONGITUDE.values, data.LATITUDE.values, data.ELEVATION.values)
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Can melting fraction of lower crust (SiO2 of 58%) reach to 40%-50%, when the mantle-derived activities are extensive?
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Although I assume it's a possibility to have such a high degree of partial melting, I wonder about Sobhi Nasir's answer that one would expect to get melts with over 80% SiO2. What is that number based on, experimental work? It sounds rather high to me.
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Different methods are used for enhanced oil recovery. But, as the impact of natural factors?
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Vagif salam!
Without hesitation, geodynamic situation strongly influences to hydrocarbon deposit generation and its preservation. For instance, geological conditions in the Dead Sea Basin are very favorable for large oil deposits accumulation. At the same time non-stable geodynamic pattern and active seismology do not assist to hydrocarbon deposit safety. Therefore, several drilled boreholes in this area discovered only signatures of hydrocarbons.
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Gigi A. Richard, Ph.D.
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Dear madam,
Actually, my research is on river morphology. Which means, it will consider the river will be migrated in such a time
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Hello,
The Zr melt concentrations in the Laacher See Magma Reservoir have been estimated by Hans Schmincke and coworkers to be in the range of hundreds of ppm (ULST), O(1000ppm) (MLST) and around 3000 ppm (LST) for the lower H20-undersaturated, middle, and upper H20-saturated compositionally zoned magma chamber respectively.
I wonder how this may relate to Zircon saturation curves. Such curves have occasionnally been constrained experimentally for certain magma compositions (work by Mark Harrison, Bruce Watson and coworkers) but I am finding it difficult to translate how this may relate to the case of the Laacher See magmas.
Zircon solubility appears to be related to Zr concentration, Temperature and magma composition including SiO2 and TiO2 concentrations and the alkali/alumina index (eg. Harrison et al 2007) and one may also expect that it  also depends on the amount of dissolved volatiles (eg. water) in the melt.
I cannot find relevant papers which would enable to assess for what conditions Zircon saturation may be reached for the 3 end-member compositions of the zoned Laacher See magma chamber (or in a presumed basanite parent magma at LSE).
What intrigues me is that Zr contents seem to me to be very high at Laacher, yet Zircon occurrence seems to be "rare" and restricted to mostly very small zircon crystals in LST pumices and to some rare occurrences of sometimes  larger crystals (typically mm-sized xtals) in some cumulate nodules from LLST and MLST (eg. Schmitt 2006).
Is it that a large melt  H20 content suppresses Zircon crystallisation ?
Or that Zircon crystallization rates are too low in general in the LSE magma conditions  ?
I would be grateful for any insights into Zircon saturation and Zircon crystallization rates and what may control them at Laacher See (P: 115-200 MPa; H20: 2.5-5.7 vol% or so), or in basanite-tephrite magmas under crustal conditions.
I am also interested in any insights for Thorite crystallization in LSE magma conditions or in basanite-tephrite magmas under crustal conditions.
Thank you in advance for any suggestions or insights.
Happy New Year and Best Wishes,
Gerald
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Dear Gerhard,  Thanks a lot for all these info. Regarding the large Laacher See zircons, I fully agree with your pegmatite hypothesis and I have scanned a photo of a zircon that supports this - indeed you have already suggested similar observations you have made yourself. On the other hand for the large zircons in the older tephrite lavas I am less convinced that the same process could work (no obvious resorbption features). I'll attach the two scans to illustrate the contrast asap, in the coming days most probably.
Thanks again for the discussion and for the ref.
Beste Grüsse,
Gerald
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its there a geochemical protolith reason? and in which geodynamic stage could this protolith forms?
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Characteristic of eclogites is the absence of plagioclase, whose albite-component is incorporated as jadeite in the omphacite. The anorthite-component is incorporated in the form of grossular-component in garnet. The transition from the loose framework structure of plagioclase (tectosilicate) changes into the close-packed structure of the chainsilicate omphacite and the nesosilicate garnet, with an eclogite-density of about 3.5. Each aluminum oversaturation in the eclogite protolith, which can not be incorporated in garnet and omphacite, crystallized in the eclogite as kyanite (nesosilicate).
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I would like to dialogue with someone familiar with programming in XOJO (formerly RealBasic).  I am an old VisualBasic programmer, and need some help with  code to read external files (common delimited variable lists) and write external files (also common delimited variable lists). Some sample code would be great! I've attached a program (zipped archive) that I've written to help with some paleomagnetic research. I need to write a batch version of this program.
Thanks!
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Tyrone,
I have been writing lots of XOJO code now that I got the I/O problem figured out.
There is one other thing that I appreciate your help with.  I can use the dialog method to open and save files interactively.  But I'd also like to open and save files directly to a folder without going through the dialogue box.  How do I tell my program (in code) to go to a specific folder and open or save a file there?  In old VB,  I simply entered all the directory routing info, but am not sure what that would look like in XOJO (for a Mac running OSX).
Thanks for any advice you can give.
Best Wishes for the holidays,     Chris
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Why such a long gap in the ages of same rock sample? Can anyone please suggest any good paper I can look into? 
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Thank You very much Marwan Wartes
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In my project area the Bastard reef is not continuous and rather grades into a melanorite. The chrome stringer is still seen at the bottom contact of the melanorite which makes people acknowledge the unit as a Bastard pyroxenite.
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Though I have not looked at the specific area you are referring to the changes in the lithologies in layered intrusions result from fractionation where the magma becomes  gradually depleted in mafic minerals and enriched in silicate minerals. if in the system you still had the hydrothermal fluids that form complexes with the Cr that would form the stringers which would settle at the bottom of the each  cyclic unit.
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 In most of my samples stretching lineations are subparallel to the dip of c-planes. However,I have some samples where pucker axis lineations within mylonitic metapelites are stretched in a direction which is sub-parallel to the  strike of mylonitic c-planes giving rise to very prominent stretching lineations. In the latter case, can I suspect greater involvement of pure shear which produced the  stretching lineations and c-planes both at the same time??
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Dear Nirmalya,
S and C planes (or shear bands as they used to be called) may display variable angles to one another, especially as they are traced into areas of higher strain. The intersection of s and C planes may also rotate into higher strain areas (perhaps producing some of the relationships you describe). In addition, new sets of shear bands develop that overprint the older rotated sets. I wrote a paper many years ago looking at geometric relationships between S-C fabrics (shear bands), mineral lineations, and rotation of c intersections (see attachment).
Note also that layer-normal differential shearing may cause extensional structures (including S-C fabrics) to develop obliquely to the overall transport direction marked by the mineral lineations (Check out Fig. 2 of the attached Alsop & Holdsworth 2007 paper)
I hope this may help.
Ian
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Why should we put the early marine strata unit in the foreland basin system (peripheral foreland basin)? I am wonder when a basin can be named foreland basin, before the final collision or after? If it is post-collision, what is the difference between the marine strata bearing forleand basin and the remnant oceanic basin?
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Dear Longgang,
The formation of a foreland basin starts during the continent-continent collision when one of the two continental plates starts to be subducted by the obducted plate. The continent-continent collision starts after closure of the remnant ocean. Accordingly, the foreland basin develops not before or after, but during the collison. The sedimentation into the foreland basin occurs during the rise of the newly forming mountain range. The reasons for intense sedimentation into the forelland basin are the intense erosion in the rising mountains and the increasing relief between the rising mountains and the descending foreland basin. If marin or terrestrial sedimentation occurs in the foreland basin is controlled by the relative sea-level and the tectonic conditions. If the grade of mountain rise is high, the subsidence in the foreland bain is also high and marin transgression into the foreland basin may occur if the relative sea-level is high.
The sedimentation in the closing but stll deep ocean before the collision is dominated by deep-marin deposits ("Flysch") whereas sedimentation into the foreland basin is dominated by shallow marine conditions. Characteristic for marine foreland basin deposist are shallow marine siliciclastic deposits in the basin and deltaic fan conglomerates around the rims of the basin.
All the best,
Elmar
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If we want to develop an analogue or numerical material for the simulation of coupled fault & fracture processes during brittle geological deformation on outcrop or structural scale what is the minimum set of rock parameters required to characterise material rheology?
Fundamental parameters: density, Poisson ratio
For fault processes: internal "peak" friction, stable and dynamic friction, cohesion, shear strength
For fracture processes: Young modulus, tensile strength, compressive strength
Would these parameters be sufficient to properly scale or define analogue/numerical materials to define the key characteristics for coupled fault-fracture processes in natural rocks? What else is required or not?
Please share you ideas.
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Dear Xiaojun Feng. We consider the weakening ratio by calculating strain softening for the undeformed rock (peak friction - dynamic friction) and for reactivation of the shear zone (stable friction - dynamic friction). I expect this is describing the same parameters you suggested. You can see our workflow for frictional parameters ingranular materials in Lohrmann et al. 2003. Do you consider the weaking ratio as similar parameter or a different one?
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Can we use a euler pole estimated using ITRF2000 to transform another set of velocities defined in ITRF2008?
or
Is Euler pole independent of the ITRF used during processing stage?
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Dear Parkash
The Euler Pole estimation correspond to the Helmert-type velocity transformation model using only rotational rates. Euler Pole Parameters have one-by-one dependency to rotational rates about the three axes.
In my opinion, use the Helmert type transformation model using shift and rotational rates (not scale).
Regards!
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Can anyone explain why Reduction to pole(RTP) value of total magnetic field deviates after a certain limit of total magnetic field(very high magnetic anomaly) ..that is calculated from magnetic field calculator for determining inclination and declination which is used for RTP calculation ? RTP  basically reduces the anomalies to those that would be observed at Magnetic north pole with a vertical remnant magnetization direction?? Explain the reasons in detail??
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The NUMERICAL problem is that the "reduction to pole" filter has a divisor which gets smaller as you get nearer to zero magnetic inclination (i.e. near the geomagnetic equator), and becomes zero at zero inclination. So RTP is unstable at inclinations less than about 20 degrees and infinite at zero inclination. Some commercial software has a stabilisation technique which is somewhat effective, but there's no TRUE solution.
The PHYSICAL problem is that 2D source bodies with strike exactly aligned N-S have zero induced magnetic anomaly at zero geomagnetic inclination. And there's no filter that can make "something" out of "nothing".
The PHYSICAL and NUMERICAL descriptions are really different ways if stating the same thing.
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The source parameter of an earthquake ( like Moment (Mo), stress drop (sigma), source radius (r), Magnitude (Mw) etc.) can be derived simply from the corner frequency of the recorded seismogram.
Questions...
1.) why corner frequency is so important in calculation of source parameters as compared to the strength (magnitude) of the frequency content of the seismogram?
2.) The seismogram records only a fraction of the energy released by an earthquake. Is it correct to estimate moment/magnitude/energy/source radius etc. from the recorded seismogram?
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I think you should read a text book. These things are explained. The corner frequency is important because this is the peak of energy radiated (you see this when you consider the power spectrum) and like an antenna radiates best at is own dimension the wave length corresponding the the corner frequency is approximately equal to the source dimension.
The moment can be estimated from the low frequency constant amplitude of the displacement spectrum from the amplitude of any frequency because at these long wavelength the source can be modeled as a point.
Of course you can estimated the energy radiated seismically by integrating first the energy at one station in the spectrum and then integrate in space considering the variations of amplitudes according to the fault plane solution, and then you need to add the energy in the P and the S-waves. After that you would have the energy radiated, but would know nothing about the energy that went into heating the fault plane by friction and the energy possibly used to break rocks, plus there is also the potential energy stored by uplift,
As I said, it's best to study a text book, perhaps Aki and Richard.
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I want to learn about the influence of oxygen fugacity on arc mamgma and its relation to the formation of porphyry deposits. Can someone recommend some articles on this topic to me. Thanks a lot.
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Dear Mr. Ze-Zhou Wang,
I think this is a very ambitious project and I agree with you that with regard to the derivation of rare elements there is still room for a lot of work. So far, the studies using Zn, Cu, and Ba isotopes are already at the beginning and many aspects obviously have not fully been understood. I would like to give you a piece of advice, try and keep in touch from the early beginning with the geology. I saw too many projects and papers ending up as a "flying carpet" . A highly sophisticated method well done but its data fraught with difficulties when in comes to the interpretation is not unsusual. I wish you all the best. Feel free to contact me through RG.
I hope my piec of  advice will help you better find your way.
Harald G. Dill
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The research for PGE (Platinum Group Elements) in mafic ultramafic igneous bodies are properly done in thick (3000 to 4000 m) bodies. The question is: when you start to consider a thick sill as a possible reservoir of ultramafic cumulates? In the bibliographic research I've done, for instance, in sills with less than 300 metres some mineral fractionation may occur, but not to produce ultramafic cumulates. 
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I have found accumulation of olivine and pyroxene from a high-Mg basaltic magma (12-13% MgO) in sills as thin as 4m. However, these are not true ultramafic rocks, they are olivine-chromite-enriched melagabbronorites. They also contain minor disseminated sulphides (pyrrhotite-pentlandite-chalcopyrite) which probably formed by contamination of the magma at an earlier stage. These sulphides could possibly contain trace amounts of Pt-Pd sulphides or other PG minerals.
To consider the question of whether the sills nearby to your hydrothermal Pt-Pd deposits could have provided the initial concentration of PGE, there are many things to consider along with the thickness. There is also the stage at which S-saturation occurred (early or late), the sequence of mineral crystallization (olivine-pyroxene-plagioclase, or olivine-plagioclase-pyroxene) and the temperature of magma emplacement (supraliquidus, liquidus, or as a cool, crystal-charged mush).
In order to provide a source for the hydrothermal enrichments, I think that these sills would have to have been emplaced in either a S-undersaturated state, in which case the PGE would have been widely distributed throughout the sill and only weakly concentrated in any mafic-ultramafic cumulate basal layer, or that they were emplaced in a sulphur saturated state, but with the immiscible sulphide droplets still entrained with the magma. In that case, the PGE would all be concentrated into the sulphide droplets, which would be themselves concentrated towards the base of the sills together with olivine-chromite-pyroxene cumulates. The worst case (for pre-enrichment of the PGE in the sills) would be if the magma was already S-saturated, but it had left all or most of the sulphides behind at a deeper level. In that case, the sills would be depleted in the PGE, and would be no better as a source rock for the hydrothermal Pt-Pd than any other crustal rocks like granites, granite-gneisses etc.
Another thing to consider would be the hydrothermal pathways - are the sills themselves or their basal contacts a locus for shearing or any other type of structure permitting fluid ingress?
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I can only find publications on dykes of the single regions surrounding the North Atlantic, but not a map summarizing all dykes. Is there a good compilation in the literature? Something like in the link?
Thanks
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Wall et al. 2010 from Basin research
Cheers
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It seems that in a fossil orogenic belt, like the famous Sulu-Dabie orogenic belt, both orogenic delamination and slab breakoff have proposed to them. Which one is more plausible?  How can we tell which process might have been responsible for a specific fossil orogenic belt if both HP-UHP metamorphic rocks and syn- and post-orogenic magmatic rocks occur there?
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The difference lies in the nature of the lithosphere. In breakoff, the subducted oceanic lithosphere is fragmented and falls into the asthenosphere, whereas in orogenic delamination, the base of the continental lithosphere is laminated and falls into the asthenosphere. The first is at the end of the subduction while the latter usually happens at the end of the collision.
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Working at the southern Central Andes we have found some interesting features. In the hinge zone of a broad (ca. 6 km) basement-cored anticline there are sub-vertical clastic dikes of breccia cutting the sequence. The basement is composed by Paleozoic metamorphic rocks and granites and is cropping out several km away from the dikes outcrop. It is covered by Jurassic volcanics of the syn-rift stage of the Neuquén basin. The dikes have between 1 and 3 meters wide and are not oriented in none particular strike. The breccia is composed by basement and syn-rift volcanics angular clasts and boulders ranging from 1 cm up to 50 cm. We are working with the structural data obtained from field work and are interested in any reference we can use to better understand their genesis. The timing of the intrusion is not clearly related with folding, it could be more related with a prior extensional stage in the region...
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I also just remembered of this Clastic Detritus blog:
No idea if it has been published a bit more
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I am trying to reduce a wealth of crystallographically determined vorticity vector orientations from some sample suites, some of which are known to have been deformed in a triclinic system. For some of the samples (deformation geometry is not known for all of them), the vorticity vector does not lie in the foliation plane (I am inferring that the foliation approximates the flow plane, which may not be the case). I understand that is predicted (and observed) that vorticity vectors can be oblique to lineation orientations in triclinic deformation. However, is it permissible that the vorticity vector lie outside of the foliation plane in certain deformations?
thanks.
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see Talbot C.J., 2014b Empirical Paths of Poles to Planes (eppps) in shear zones. Journal of Structural Geology, 66, 309-333
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I would like to distinguish these two lithologies to show a geochemical contrast between them in a figure. The figure presents a cross section through an oceanic core complex. The cross section is perpendicular to the ridge axis. 
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Jakub,
It is rather difficult, at least for me, to reply to you answer, that appears to be too generic to be answered with a simple and clear statement on the state of art on you problem.
I give to you some informations that are based on my experience of the natural laboratory of the ophiolitic peridotites from the Alps and Apennines (N-W Italy), and, accordingly concern the rifting stages of opening of the fossil Jurassic slow-ultraslow Ligurian Tethys basin.
I can say that :
1) lherzolites (and particularly fertile spinel – to plagioclase lherzolites), most probably derived from the sub-continental mantle lithosphere during the rifting stages of the basin, are exhumed and eventually exposed at the sea-floor close to the Ocean-Continent Transition (OCT) Zones of the rifted margins;
2) harzburgites (and, particularly. depleted reactive spinel harzburgites) frequently associated to large volumes of impregnated plagioclase peridotites, progressively replace sub-continental lherzolites ocean-wards. They are interpreted as products of melt/peridotite reaction caused by porous flow infiltration and percolation of early asthenospheric melts during the pre-oceanic magmatic rifting stages of the future basin.
3) refractory harzburgites, formed by oceanic partial melting and parental to the subsequent oceanic MORB magmatism of the basin, are doubtly described at the sea-floor during the embryonic stages of oceanic spreading.
In our cases, evident chemical contrast exist between fertile lherzolites, reactively depleted harzburgites and refertilized plagioclase peridotites, depending on the processes of formation, both melting and melt/rock interaction.
I don’t know if more informations on these situations and geodynamic settings are useful to your problem.
In the case, write again and I’ll give you appropriated references.
Giovanni
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I am looking to find a code to compute the viscoelastic deformation of a beam over a fluid, in order to compute the time dependant flexure of the lithosphere under a load.
Can anyone suggest an easy way to do this? Is it possible to do it for a broken and an infinite beam (like in regional isostasy)? Is it posible to do it with variable Te?
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Hi Mariano,
You can also try Pylith. I've been working with this FEM code for a while now and it's very straight forward and easy to set up. You can generate complex geometries and it will handle viscoelastic materials. I don't know if it is the best option for GIA (if that's what you are trying to do), but you may want to take a look at it: http://geodynamics.org/cig/software/pylith/ The documentation is fairly good, but I don't know if you'll find the stiffness matrix definitions.
You'll also need to develop your FEM model. There are several ways. You can use a trial version of Trelis: http://www.csimsoft.com/trelis-fea.jsp. This program will let you generate pretty complex models, but it's not free. Look into Pylith's manual to find other free options to develop simpler FEM models.
Good luck, y saludos.
Demián
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Seamount subduction has been well studied especially since 2000 (Kodaira et al.). In some cases such as the 1946 Nankai earthquake (Mw 8.2), it has been suggested that seamounts act as a barrier and hence prevent earthquake rupture due to weak coupling. On the other hand Husen et al (2002), suggest that seamount acted as an asperity (and hence strong interplate coupling) in the 1990 Gulf of Nicoya earthquake (Mw 7). Is the debate still open or a conclusion has been reached on the role subducted seamounts play in earthquake generation?
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I suppose, that subducting seamounts induce weak interplate coupling,  but they can sometimes result in the change of the subduction regime and to be the cause of the slabe break-up as we can see in west Pacific near south Kuril and north Japan.
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The strain at depth   will induced stress at  subsequent shallower depth and this process will continue until it is released at the surface.
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I don't know very well the topic but it is very interesting for me too.
In my region (Emilia, Italy)  an earthquake happened in 2012 and it was and is still studied (e.g., Annals of Geophysics 55/4, 2012 and subsequent papers on international journals).
If you will search among the italian INGV (National Institute of Geophysics and volcanology) contributions you will find surely something matching your interests.
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