Questions related to Geological Processes
I am looking for references about geological process rates to highlight the differences between average rates and episodic rates for teaching purposes. Does anyone know some references? Thank you
My objective is to model the stress-relief mechanism of a clayey meter scale experiment.
Please, share published material and your suggestions for such a small scale experiment.
I understand metasomatism as follows:-
1. It is a geological process which involves the transfer of fluid energy and materials to a new rock system.
2. It always involves contribution of new chemical materials to the intruded and interacted system.
3. It can changes the mineralogy, texture, geochemistry and isotopes of pre-existing rocks during its intrusion and interaction.
4. It is an igneous metasomatic process when the last remaining fluid portion of a crystallizing magma escapes and interacts with the earlier formed rocks.
5. It is a metamorphic metasomatic process when chemically active fluids are expelled out of pre-existing rocks through the rise of pressure-temperature conditions, and then which accumulates to interact with the rocks.
Thank you very much in advance.
I am looking for template for the Ti in zircon geothermometer. Can someone help with an excel spreadsheet please?
Only Japan and China have been successful so far in extracting methane from gas-hydrate fields, albeit the fact that nearly 40 countries have carried out marine gas-hydrate explorations:
Why is it so?
What are the highly sensitive geological processes that might trigger hazardous situations before, during and after the gas-hydrate production tests?
We have here a small granite stock with an apparently abnormal composition, for which we have not yet a real clue how it originated. The granite is highly evolved, high-K, weakly peraluminous (77 wt% SiO2, 0.06 wt% TiO2, 0.01 MgO, 0.15 CaO, < 0.01 P2O5, Sr < 10 ppm, Co, Ni < 1 ppm etc.). The most interesting feature, however, is the chondritic Nb/Ta ratio of 17.5 (Nb ~ 55 ppm), which is exactly the opposite to what is expected for an evolved granite. Radioactive isotopes imply that the granite is entirely crustal. No field evidence exists that the granite is part of a composite pluton containing less evolved members, i.e., has received its compositional signatures as result of fractional-crystallization differentiation. Thus, the source rock should also be felsic.
Has anybody an idea how such a rock may have generated? What might have been the protolith for this type of granite?
I found some clathrates in fluid inclusions in the fluorite. But what is the significance? Some articles suggest the clathrates present overpressure. really? The temperature of the inclusion in the photograph is 6.0℃.
Kindly, could any one let me know how to fix the value of concavity index (-0.4) when use TecDEM software. fixing this value is very important to extract the steepness index which could be depend on in the evaluation of tectonics?
In convergent margins as the arc setting evolve from oceanic to continental arc, metal endowment also may change; for instance, Cu+Au and Cu+Mo porphyry type deposits are predominant in oceanic island arcs and continental arcs, respectively.
However in a single setting, such as a continental arc, special types of deposits may be predominant in some parts. If the age of mineralization be almost similar along the arc (e.g. middle to late Miocene), what other factors control this diversity?
I have observed that sometimes a granite, by its essential mineralogy, doesn't contain any kind of accessory minerals.
No single grain of opaque/ transparent accessory minerals which normally occurs in a granite.
what makes them so cleared off with respect to any kind of accessory minerals?
Is it original composition of magma?
is it due to certain physico-chemical conditions/ tectonic setting?
Fuchsite (chromian muscovite) or other chromian silicates are common as the result of metamorphism on ultramafic-mafic protoliths. Hence their occurrence in orogenic gold deposits. However, we have found it as a hydrothermal mineral in IOGC deposits (so far, two of them) in areas in which ultramafic-mafic rock are still unheard of. Please see discussion in the following link:
Has anyone found fuchsite in similar environments? Any idea of its geological implications? Thanks!
Some of the zircons bear positive Eu anomaly which i think may be altered magmatic zircons, because the samples is from an altered zone.
Yes, the fluid inclusions of halite can express some important information of paleoseawater in some degree. They can only indicate the components of paleoseawater in that time, but can`t reflect why the components of paleoseawater was so, can`t reflect what process the paleoseawater experienced.
I think the fluid inclusions of halite in some evaporite deposits just can indicate the changes of paleoseawater in that basin in that time, besides, the paleoseawater in that basin in that time may have exchanged with many sources. They can`t indicate the whole and homogeneous components of paleoseawater in that time.
There still need to find new evidences in primary marine stratum in closed basin unmodification.
Well, I have a small question, did anyone knows how to calculate the model (lattice-strain) for the parenting fluid responsible of a fluorite mineralization besides the derived and calculated fluid from the supposed source, using data from Rare Earth Elements (REE),
thank you so much,
P.S: it will be more easy if someone could provide me with Excel file, thanks
The so-called hydrothermally altered zircons, what makes it diffrent from hydrothermal zircons. What is the implication of alteration in zircons in mineral genesis. it is kind of complicated
On a Y+Nb vs. Rb classification diagram (Pearce et al., 1984; Pearce, 1996), all of the Late Mesoproterozoic hornblede gabbros plot in the volcanic arc granitoid fields. Why did not show Nb-Ta trough. In contrast, the ca. 1222 Ma quartz diorites plot in the within-plate granitoid fields.
Add: The Late Mesoproterozoic mafic intrusive rocks intruded in southwestern part of the Dongman Island in the central-western marginal area of the Korean Peninsula. The mafic intrusive rocks exposed in a NW-SE trending body with ca. 20 m in width and ca. 250 m in length. They consist mainly of the predominant fine- to medium-grained gabbro (ca. 1259 Ma) with minor medium- to coarse-grained quartz monzodiorite (ca. 1222 Ma) and mafic dyke. The ca. 1259 Ma gabbro shows weakly to strongly foliation. It consists of hornblende (40–55%), plagioclase (40–45%), K-feldspar (2–5%), quartz (0–2%) and biotite (3–5%). The ca. 1222 Ma quartz diorite occur intrusively in the gabbro body. Some diorites include gabbro xenoliths. In the boundary between diorite and gabbro, quartz monzodiorite invades along the cracks of gabbro and occur magma melts walls of gabbro reflecting assimilation. The quartz monzodiorite consists of plagioclase (45–55%), hornblende (15–25%), K-feldspar (8–12%), quartz (7–10%) and biotite (5–15%).
I'm a PhD student in Geological Sciences and I'm looking at access a HIP to try to sinter natural volcanic materials for tens of hours to days at temperatures up to 900 C and confining pressures up to 25 MPa.
Do any of you know of universities, research groups or facilities with a HIP that would be interested in collaborating on this project?
For example, in some granite samples (low-T I- and S-types), there are lots of zircon cores and grains with U-Pb ages older than emplaced ages of the granites. How to distinguish the inherited zircon from the zircon xenocryst?
This is an excellent paper. It contributes both valuable new data and solid interpretations of the origin of Nyakabingo, one of the Rwanda-Uganda “tungsten belt deposits”and its relations to rare-metal pegmatite formation.
The authors demonstrate by geochemical data the long-assumed connex between parental ca. 1000 Ma so-called G4 granites, tin and tantalum mineralized pegmatites (at Gatumba) and the wolframite-quartz veins at Nyakabingo. Considering the distance of 70 km between the two, a direct flow of liquids and fluids between the Sn and W districts is not insinuated. The assumption is that in both cases, differentiation and fractionation of G4 granite produced mineralizing residual liquids and/or fluids. The “text-book” model of the relation between pegmatites and hydrothermal mineralization predicts that the second should follow the first.
The authors used muscovite trace geochemistry to determine and compare the degree of differentiation/fractionation of pegmatites and W-ore veins. Curiously, these data imply that the tungsten mineralizing fluids were expelled at the same fractionation stage as early unmineralized pegmatites.
How is this to be explained? I wonder if the solution would not be the contemporaneous tectonic deformation!
My own mapping of the tungsten belt deposits Bugarama and Nyakabingo (with Günther & Ndutiye), and of the nearby large cassiterite vein fields of Rutongo, and of Wolfgang Frisch at Gifurwe all showed that the veins are tectonically controlled by thin-skinned folding and overthrusting. G4 melt bodies may have been disturbed by tectonic deformation, from a state of quiet fractionation and differentiation to sudden pressure changes and deformation of the whole melt body as the country rocks heaved.
“Typically in the Kibara belt, pathways and traps for pegmatite melts, or for metalliferous
hydrothermal fluids, were low-pressure hinge zones of tightening anticlinal folds with axial
planes or cleavage planes on the flanks of folds as feeder and break-through structures. The
compressive stress field was rotated compared to the Mesoproterozoic main deformation and produced fold axes and thrusts cutting earlier folds at sharp to orthogonal angles. Outcrop patterns created by fold interference are visible on geological maps; resulting highs often determined the location of tin granite cupolas or ridges and associated deposits” (citation from Pohl et al. 2014; for research use, I can provide a PDF).
The cause for both the compressive tectonics and the crustal melting that produced the G4 granite suite were the ca. 1 Ga global tectono-magmatic events of the final assembly of Supercontinent Rodinia (the “pan-Rodinian orogenic events” of Li et al. 2008).
Would you agree?
Barren Measures are sandwiched between two thick coal bearing formations i.e. Barakar and Raniganj, and devoid of coals. What are the reasons for the sudden extinction and reappearance of coal in reference to global tectonic and environment?
I am working on zircons of granitoids where the isolated zircon grains largely show oscillatory zoning revealed in CL images. My immediate attention to experts is that if those zircons originated by the magmatic processes or not?
I'm studying a Late Cretaceous (~68 Ma) opx-bearing granite in the Qiangtang Terrane, Tibetan Plateau. The two-pyroxene barametry indicates that the melt-formation of the this pluton require pressure ≥ 14.2–18.1 kbar and temperature ≥ 900–1000 ℃. When plotted on the P-T diagram illustrating the partial melting of mafic lower crust and phase relationship, this P-T range corresponds to the “amphibole and plagioclase-out” and “garnet-in” field, implying the breakdown of amphiboles and plagioclases and occurrence of garnets in the source region.
In combination of chemical compositions, we suggest that partial melting of mafic lower continental crust in the stability of garnet (e.g., garnet-granulites or eclogites) was the most plausible scenario for the genesis of the pluton. High Sr and Ba, low Y and heavy rare earth elements (REEs), strong depletion of high-field-strength elements (HFSEs) such as Nb, Ta and Ti, and lack of negative Sr and Eu anomalies (Martin 1986, 1999; Defant and Drummond 1990; Martin et al. 2005) in the rocks indicate that the pluton closely resembles adakites in element compositions. However, peculiarly, it exhibits higher Yb and Y concentrations as well as lower Sr/Y and (La/Yb)N ratios relative to the typical adakites.
It is so peculiar. So, I want to ask partial melting of garnet-granulites or eclogites necessarily produces adakites with high Sr/Y and (La/Yb)n ratios? If not, what geological processes would result into the decrease of these two ratios in the partial melts from the eclogites or garnrt-bearing granulites?
I read this paper from Butler and Paton (Butler R.W.H., Paton D.A., 2010. Evaluating lateral compaction in deepwater fold and thrust belts: How much are we missing from “nature’s sandbox”?, GSA today, v.2 , n° 3, 7pp, 4-10, doi : 10.1130/GSATG77A.1) that shows on the Namibian margin how shortening related to gravity gliding can be accommodated by direct lateral compaction within the sedimentary layers. Lateral compaction could thus accommodate 18 to 25% of the shortening and then the amount of shortening evidenced by the reverse faults is lower than the true shortening.
Do you know other examples/references concerning lateral compaction process?
Does a low amount of shortening (say less than 25%) could be entirely accommodated by lateral compaction within the sedimentary layer, then without any reverse fault?
Many thanks in advance!
This picture is published in the web site of the Amazing Geologist. Can any one reconstitute the paleohistoir of this region?
A 1.9 Ga metamorphism existed in North China. In the khodalite belt, there is a consensus that the metamorphism is a product of subduction. But for the middle and east part, why people say when metamorphism happened, the orogeny process initiated? So, I am confused and wondered other cases. Welcome to any idea. Thank you in advance.
We Know Nb and Ta are usually coupled in most geological processes. However, in my a recent study on a granitoid, I observe the decoupling between elements Nb and Ta. In the samples, element Nb is obviously depleted whereas Ta is variable in content from highly depleted to slightly enriched. I want to ask what geological process leads to Ta decoupled from Nb in granitoid? Fluid contamination or fractional crystallization of both major phases and accessory phases?
A spider diagram is attached here.
Thanks. With regards.
basaltic melt production from metasomatized mantle is common feature of subduction zones. I want to know if high degree partial melting has occured in Deep Crustal Hot Zones, the basaltic melt likewise can be produced?
I am doing a Project based on xenoliths and megacrysts in kimberlites based on the Monastery mine and other mines in the Free State, South Africa; and would like to know if there are any journals, books, any research work available to look at. I have realized that most research work on acquiring information about the crust and mantle has been mainly focused on using mantle xenoliths as compared to crustal xenoliths. If any, i would love to acquire more information about crustal xenoliths in general as this is also part of my project.
I need a sampling device to get relatively undisturbed samples from soft sediment habitats in fjords, which can be operated from a relatively small vessel (multicorer is too large). The Gemini corer seems to be suitable, but I cannot find a supplier. I think it was often used in Russia and Finland. Thanks for your help!
Dear all, what I whant to know is - if a herbivorous mammal species crossed the area of modern Sea of Marmara, would this species face something new? I mean, the distance is not so long... Could there be more or less significant differences? To make such a comparison myself using different articles of different authors seems to me unreliable. Different authors use different approaches...
What are the effects of these fluids on partial melting degree of rocks? Why do the rocks' partial melting degree decrease?
I would like to ask that is there any quantitative index to describe the complexity of geological conditions for the purpose of risk assessment in mining or construction.
I am looking to find a relation between potential source rock thickness and the migration path of Hydrocarbon and volume in reservoir Rock.
Flow of rivers are not only affected by the size and slopes but also of its geometry. Used several software but most do not consider river sinuosity in the calculation.
The O18 isotopic equilibrium temperature (between biotite-muscovite) in a metapelitic mylonite is 300 deg C. However, the stable paragenesis of these metapelites includes garnet, staurolite. The Ar-Ar age of recrystallized muscovite is 11-13 Ma. Can we say that ductile deformation related to mylonitization occurred 11-13 Ma?..Or is it the just the cooling age of the pelites which have undergone garnet and staurolite stable metamorphism earlier? What are the constraints??
Hi, I am working with pull apart basins and I would like to know if there is any work that relates the size of the basin with the offset of the transform plate boundary. For example, offset vs basin length.
For Na-montmorillonite, experiment has not detected cation solvation by CO2 in the interlayer, even for dry Na-montmorillonite. Why? It happens in dry zeolites, why not montmorillonite?
What is the typical angle of inclination for dunes formed by fluvial processes? And is there any reference discusses that.
Is there any reference explains the difference between aeolian dunes and fluvial dunes in term of the angle of repose and inclination. Thanks.
I would like to kindly have your opinion on this matter. Here is a couple of polarization microscope snaps (scale is on the snaps). Does any of these qualify as a planar deformation feature (PDF)? Thank you for your ongoing support. I am sorry for the bad quality. It is the best the camera can do.
Why I do not think they are PDFs:
- Some of them cross several grains
- They might be preparation artifacts
Why I think they might be PDFs:
- They only occur in a small region near the crater
- They have different orientations
- They only occur in the highest shocked sample (the other less shocked samples were prepared in the same exact manner)
Thank you in advance, looking forward to your replies! :D
Can the following processes happen?
1 Long term of oceanic subduction took place at first.
2 Afterwards, due to slab roll-back or slab breakoff, the tectonic setting switch from compression to extension.
3 After a period, the subduction cease.
If it is not feasible, can you give me some other possibilities that active continental margin can be transformed to passive continental margin?
please can you help me to know about this bioturbation which I found it in lower callovien of algeria
Absolute dating is necessary for knowing specific time e.g. by isotope K/Ar in mica, especially in the crystalline rock: igneous and metamorphic rock. On the other hand, the sedimentary rock (as I know) usually provide the time of formation by age range of fossil e.g. Upper Miocene - Piocene. Is there any method to make it more specific like the crystalline one?
This article published (where?) by Stanislaw Halas et al, 2013, discusses stable isotopic values in authigenic quartz crystals that are supposedly co-precipitated in halite crystals. However, to me, it looks as if the researchers forget that authigenic quartz precipitates from hydrothermal liquids at higher temperatures (200 - 400 C). If they are found inside halite crystals, it means that also these crystals likely precipitated at high temperatures, such as is documented in the Afar region, see attached article.
Highly matured Permian sediments (0.6%vro) occurr at shallow depth(~300m). Why is that? How is the tectonic history related to thermal history in these basins? What are the geological ages of different tectonic phases?
The Trans-Mexican volcanic belt is a very irregular and wide (100-500 km) active magmatic arc, but I am not sure where does it actually end. In the backarc or in the rear arc?
The late Prof. Dr. Antonio de Barros Machado, Director of the Dundo Museum of Zoology and Anthropology in Angola (1947-1974) studied during more than 30 years of intense work (until 2003 in Portugal, Oeiras) a great number of laterite and bauxite rock samples, in his opinion molded by termite activity in geologic times. He analyzed laterite and bauxite rocks from many places on Earth. His results were only partially recognized because they put into question the "sedimentary origin" of theses formations. I have been dealing with his heritage and am ready to bridge important data for interested colleagues. Grasset mentions in his double volumed encyclopedia part, dedicated to termites, that he never had met more convincing arguments as to the origin of these rocks then those of Barros Machado, though in his first approach, documented in the earlier Zoology encyclopedia, he was not yet convinced, but then surrendered to the smashing amount of proof, proposed by Barros Machado.
In the collection of private letters, there were more geology scientists to accept this innovating idea, but it still remains controverse.
The figure shows EPMA data of clinopyroxene fragments in a subaqueous basaltic tuff. The tuff, as interlayer of radiolarian chert, is part of the circum-Pacific accretionary complex. It mainly consists of well-sorted angular vitreous and crystal (mostly clinopyroxene) fragments and geochemically belongs to OIB type. The analytical sites are on different clinopyroxene fragments located at a small area about 2cm*2cm.
The linear trends of MgO, TiO2, FeO, Mg#, Al2O3 vs. SiO2 of clinopyroxenes are very well. Based on Kushiro, 1960 and LeBAS, 1962, these trends are likely related to fractionation. However, the Al-Si trend in LeBAS, 1962 is from data of different rocks whereas here we have non-alkaline (possibly tholeiite), alkaline, and peralkaline clinopyroxenes from one tuff (one-time eruption).
What is the controlling factor of the chemical variations of clinopyroxene fragments in subaqueous basaltic tuff? What's the geological processes behind the fractionation?
This granular (Fig. 1) is found in a shard of subaqueous basaltic tuff (Fig. 2). The tuff mainly consists of clinopyroxene and chlorite mineral clasts and shard. As shown in Fig. 1 and Fig. 3, the granular has three part: the darkest rim and core is chlorite, with low SiO2, low CaO, high MgO and Fe2O3. The gray part is epidote, with high Al2O3, high CaO, and low MgO. The light ring is likely sphene, with ~30% TiO2, ~30% CaO, and ~30% SiO2.
There is a small high CaO grain in the right like a door of the high Ti-Ca ring (See the CaO distribution map), possibly calcite. Some small sphene globules ejected through the door (Fig. 1).
I am trying to explain this geological process:
The three-part chemical association was formed by chloritization of basaltic magma. The chloritization was faster than magma coolling because the seawater was heated to a very high temperature. When the chloritization (explosion and seawater-magma interact) occured, the melt was separated into chlorite, epidote, sphene and calcite, however, the granular was still hot that the core was still in liquid state. Then the sphene globules ejected into the core because of pressure difference...
Does anyone believe this? I am interested to hear your interpretations!
I am doing research in volcano sedimentary terrain of Precambrian period. I am unable to differentiate shale and tuff because of metamorphism of these rocks.
At the end of the 1990's, we compiled and published comprehensive data on the trace-element composition of trioctahedral micas (i.e., TISCHENDORF, G., FÖRSTER, H.-J. and GOTTESMANN, B. (2001a) Minor- and trace-element composition of trioctahedral micas: a review. – Mineral. Mag., vol. 64, No. 2, p. 249–276.). Unfortunately, respective data on dioctahedral micas is largely missing.
I'm working with granulites and I applied the thermometer of Ti-in-Biotite in my samples, the problem is that this is calibrated for 4-6 kbar rocks and T<800°C and I'm working with granulites of 7 Kbar and >800°C. The results I got from this thermometer are similiar with others thermometers as Ti-in-Quartz and Zr-in-Rt.
I'm looking for some information about fault/fracture network created in the host rock by the stresses induced from the intrusion of a magma body in the crust.
Explosive volcanic eruptions occurred throughout Palaeozoic time. Under the right set of circumastances they can be preserved in the sedimentary record.
The age of my metavolcanic rocks is about 2.5Ga, some of the samples have too low trace element concerntrations especially the HREE, they are even lower than the chondrite, I want to figure out what geological processes have happened?
Is there any other comprehensive work which is dealing with the terminology of layered intrusions apart from the classical paper of T. N.Irvine (1982). Terminology for layered intrusions. Journal of Petrology, 23(2), 127-162.
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?
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?
Can wind and/or water (marine environment) transport produce a mineralogical selection on volcanic tuffs deposits? Do you know any example?
Many minerals like spinel, phlogpite, olivine etc. crystallize records the magma evolutionary trends forming zoning trends; but simultaneously similar phases may give zoning due secondary or interaction with the late stage magma.
Is there any clear discrimination for these?
My problem is that clay can undergo compaction without any true crystallographic change. In consequence, how can I reliably attribute any concentration change (major or trace elements) to the smectite-to-illite transition ?
There have been many studies in recent years showing that granitoid intrusions can be built through several pulses of melt. A lot of these focus on the internal structure and timing of emplacement. Does anyone know of studies that examine the relative volumes of individual melt pulses within composition intrusions?