Questions related to Igneous Petrology
understanding research processes in igneous and metamorphic petrology.
Doing research in igneous petrology.
what are the tools and requirements for research starting before field observation and field observation and after field observation?
Igneous Petrology Scientific Research
Both alkali metasomatism (fenitization) and assimilation of silicate material may be present along the contacts zones between carbonatites and host rocks, but how to discriminate between these two processes
During the melting of a metabasaltic rock at variable depths, the Ti budget in the anatectic granitic/intermediate melt is determined by the presence of Ti bearing minerals like Titanite, rutile, ilmenite etc. in the residual and/or fractionating assemblage. How the depth of melting/pressure of melting influences the stability of these minerals?
Imagine you have some volcanic rock samples from a given area and about 30 km southwest there is an acidic pluton which is the same age as your rocks. Let's say that both your rocks and samples from the intrusion show perfect fractional crystallization trend on the La vs. La/Sm diagram with only several samples deviating from the trend line. Their common La/Sm ratio is constant, in this case, and let's say it is around 7, while La contents vary from 20 to over 60 ppm with one sample reaching up to 90 ppm. In this case, it seems reasonable to argue that they evolved together from the same source, I guess.
My question is, if we assume a hypotethical situation where the La/Sm ratio of the volcanics is, say, 25, whereas that of the samples from the acidic pluton is 7, would that imply that they evolved from different source regions?
NASICON's and their common analogues use Na, K,Li or other alkali metals, Si, P and some other relatively common metals like Al, Ti, (Fe?) etc. NASICONs are with the formula Na1+xZr2SixP3-xO12with 0<x<3 . NA, Zr, Si are replaceable with isovalent elements and beyond. For example, LiTi2(PO4)3 is also considered a NASICON analogue, so is Li1+xAlxTi2-x(PO4)3. Both Sol-gel and Ball-milling then sintering techniques an be used for NASICONs.
While there are many common minerals like ZIrconia or Moissanite that shows fast ion conductivity, they act at quite high temperature. Silica is extremely common mineral, so is alumina, and apatites are quite common in sedimentary as well as some igneous environment. While complex silicates like Zeolites can exist in nature, why not NASICONs or their some sort of analogues? Does all of them react with moisture and Carbon dioxide relatively rapidly in geological scale? If they do exist, then what kind of geological environment would be conducive to their existence?
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?
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.
Microscopic examination of a sample of low cretaceous igneous rock (alkaline bazaltoid or monchiquite?) revealed this foaming in the older generation of apatite (see photo). The central parts of apatite crystals are highly crowded with gas-liquid inclusions, the surfaces of crystals, just as younger generations are without them. Do you happen to know what that indicates? My timid guess is that it could be the release and decay of a supercritical fluid during crystallization, perhaps. I can't find anything like that in the literature.
( some fresh outcrops of amygdaloidal basalts have been found to occur near the Ophiolite Complex)
My mafic meta-volcanic rocks can be devided into two groups. Group 1 rocks are distinct from Group 2 as displayed by their markedly higher concentrations of Fe2O3T (18.5-18.6 wt.%), TiO2 (3.5 wt.%) and P2O5 (1-1.1 wt.%), lower MgO (5.1-5.2 wt.%) and lower silica contents (SiO2 = 43.6%-44.3 wt.%). And the higher concentrations of the incompatible elements (i.e., Zr, Y, Nd, Sm, Nb and P) and lower concentrations of compatible elements (i.e., Cr and Ni) in Group1 are also distinct from Group 2. These features are similar to the Fe-Ti basalts which are characterized by iron- and titanium enrichment (FeOT>12 wt.%, TiO2>2 wt.% and FeOT/MgO>1.75) but silica depletion (Sinton et al., 1983; Hunter and Sparks, 1987; Furnes et al., 1998; Jang et al., 2001; Harper, 2003; Qian et al., 2006). Because of the absence of Fe-Ti oxides phenocrysts, most researchers consider that the high concentrations of iron and titanium were not caused by the cumulus Fe-Ti oxides, and the Fe-Ti basalts are interpreted to be products of moderate to high degree of Fenner trend differentiation of basaltic magma at low oxygen fugacity (Jang et al., 2001; Xu et al., 2001; Qian et al., 2006). However, there are many Fe-Ti oxide phenocrysts in my samples, and no cumulate structures were observed in my samples. So it is hard to get the conclusion that they were formed from the cumulation process, I want to konw which process can cause this geochemical features.
Two andesitic samples have significant Tb negative anomaly. The same ones also have Pr negative anomaly which I can explain by a late apatite crystallisation and many apatite inclusions in phenocrysts. I cannot find any information on Tb.
Some rocks with appreciable amount of felsic and mafic minerals have been crushed. In order to melt the rock at low temperature and/or to leach water-soluble cations, either boric acid (H3BO3) or mono-ammonium phosphate (NH6PO4) is mixed with the crushed rock and heated.
boric acid is commercial grade and mono-ammonium phosphate is fertiliser grade. Enough provision is made to vent out ammonia. Heating source is household gas cooking oven. Container is made of cast iron. The rocks are mixed, chiefly Granite and Gabbro. i.e. holocrystalline (pegmatite?) rocks with physically discernible grains. Rocks are crushed to about 2-5 mm size, heating period is below 3 hours on open deep bowl. The heated mixture is leached with rainwater to extract the soluble minerals.
My question is, which of these two chemicals would be able to form more water-soluble cation? Or which one would cause more melting temperature drop of the flux+ crushed rock mixture? Extraction of Na, and K cations are of first priority. Please also mention the ratio of rock vs flux as well.
My samples are typically basanite and phonotephrite in composition. Mineral assemblages in some of them are similar to lamprophyric facies in which hydrous mafic minerals (such as pargasite and phlogopite) are present together with anhydrous mafic minerals (olivine and clinopyroxene) and without (or less amounts) plagioclase. Although these rocks are vesicular, I wonder if I can use “lamprophyre” term for them. Gratefully, Meysam
I am beginning my undergraduate research in a granite quarry and am attempting petrogenetic modeling. However I can't seem to find good sources with all of the partition coefficients I need for trace elements. I am using Nash, 1983, and Henderson, 1984, currently. Thank you in advance!
I am a materials science (and metallurgy) student and geology enthusiast. Comparing these two subjects side by side, I have found out some interesting pattern.
Ironmaking slag has 40-45% CaO, 30-40% SiO2 , 10-15% Al2O3 , about 5% MgO and 1-2% FeO. Steelmaking slag can have 40-60% CaO, 10-25% SiO2, 2-10% MgO, 5-35% FeO and 0-25% P2O5.
Ironmaking slag can have, among many other minerals, Akermanite, Monticellite, Gehlenite ,Anorthite, Pyroxene etc, along with some spinels. In my opinion , it matches with some feldspathoids with slightly mafic character. Steelmaking slag is more close to alkaline earth mafic rocks and peridotites. It has a good amount of spinels, monticellite, merwinite, silicocarnite, periclase etc.
Answers from metallurgists and Geologists are welcome
Can you recommend some software or articles to study?
The rock is pantellerite with main phenocrysts as amphiboles (Na and Na-Ca subroup) and intergrowth albite and sanidine.
Uncertainty in the values of eNd(t) or eHf(t) (epsilon Nd or Hf) of a particular sample (rock or mineral) depends on several things including uncertainties in the present day isotopic ratios and uncertainty of the instrument. If I have only the error values (say 2s) of present day isotopic ratios of a sample (say Sm/Nd and Nd/Nd), is it possible to propagate the error from these uncertainties alone and calculate the uncertainty in eNd(t) or epsilon Nd (initial)? If yes, can someone kindly share the any worked out calculation for it?
The study area, located in the circum-Pacific accretionary complex, mainly consists of intra-oceanic surface rocks including chert, shale, pyroclastic rocks and basaltic lava. The basaltic rocks are mostly OIB-type (Jurassic Paleo-Pacific seamount) according to previous research.
Photo 3 shows two basaltic pillows within a matrix of basaltic tuff. The handspeciman of the pillow is black in color and heavy in weight. It also has scattered vesicles, and looks much like typical fine-grained basalt. However, its thin section looks not...
I need help to identify the rock type. It will be perfect if you also have such kind of rock.
I have some selected samples with basaltic in composition and vesicular texture. All of the primary constituents are fresh, and they don't have any alteration in thin sections. However, their vesicles typically filled by zeolite, carbonate, and other secondary minerals. I want to do a geochemical analysis for them. So I want to know, there are any effective methods to eliminate these secondary minerals, especially zeolites?
Looking forward to your valuable replies. Much appreciated!
Clay samples are heated at 950 degree centigrade (LOI method) before XRF analysis. Due to which Fe percentage increases in the XRF results. It is due to the oxidation of samples during fusion. Is there any procedure to correct the Fe value within the results?
The rhyolite is a mixture of a less evolved rhyolite (or dacite) and a more evolved rhyolite. It has two kinds of Opx phenocrysts: none zoning Opx with a little bit higher Mg# and reverse zoning Opx. There are also some Ca-clinopyroxene phenocrysts. Both the Opx phenocrysts have low CaO contents (< 2 wt.%). However, the Px microlites in the rhyolites have much higher CaO (3 - 8 wt.%), which belong to pigeonite. Please see the attached picture. How are these Low Ca Cpx (Pigeonite) microlites formed? Ps: There is positive correlation between CaO and Al2O3 for those Px microlites but not for phenocrysts.
Charoite is a rare alkali silicate that occurs in an attractively looking pink-purple rock in the Murun Massive, Sakha Republic, Yakutia, Siberia. This rock is a sort of skarn generated metasomatically at the contact between the Murun Syenite and the encasing limestone. I attach a photo of my sample. Does a similar rock occur elsewhere in the world?
I found a (meta-) gabbroic sample contains some garnets, next, I want to know the genesis of these garnets (igneous or metamorphic origin). What should I do? Could I distinguish them just by their major composition? If you know that how to solve this problem, please recommend some references to me. Thank you very much.
Please upload information related to any upcoming seminar or conferences in India related to Igneous Petrology.....
Is it possible to clearly differentiate igneous to metamorphic titanite/monazite based on their REE?
e.g. Eu, CE anomaly or enrichment of HREE
can anyone suggest references?
Cooperation in igneous and metamorphic petrology and help in U/Pb dating.
I want to conduct chemistry analysis on an anonymous ultrabasic bodies. I want to adapt Mullen(1982)'s MnOX10-TiO2-P2O5X10 tertiary discrimination diagram to find its geotectonic condition. The SiO2 w.% of this ultrabasic bodies are plotted between 42%~46%. Can I use this method for my analysis?
I deal with detrital heavy minerals. I found quite numerous topaz grains in several samples. I wonder if this is possible to distinguish between different source rocks (e.g., various pegmatites and skarns from the Bohemian Massif, Central Europe) using chemical composition of the topaz grains/crystals (major and minor elements using electron microprobe, and/or trace elements using laser ablation). This subject is completely new for me, I will be grateful for any tips.
Granite powder is an Aluino-silicate material claimed by some researchers to work as geopolymer raw material. The Al:Si ratio is in the vicinity of 1:4 and not the magic ratio of 1:2. The alkaline liquid activator and the soluble sodium silicate required does not work for GP as used to work for Flay Ash.
Does a HREE depleted source explains HREE depletion itself?
HREE are commonly or exclusively garnet-controlled?
Which processes can cause different HREE content in a co genetic magma series?
Can strongly positive Eu anomaly (at least 10 times higher) be in any terms related to HREE depletion and their concave upwards pattern in a REE chondrite normalized spidergram ?
I want to do some modelling in order to see if different degrees of partial melting had (or not) some influence on the chemical variability of granite samples (in this case I-type granites, therefore, derived from partial melting of the lower crust). For this, I'm considering a batch melting process. However, I'm not sure which modal composition of the residual solid should be assumed in the calculation of bulk distribuition coefficients.
We want to compare the forming pressures of two types of rhyolites but we only have whole-rock compositions of the rhyolites. Are their any chemical index (Major elements? Trace elements? element ratios?) that could qualitatively indicate forming pressures of rhyolites?
I follow the Niggli's diagrams for the amphibloite rocks which I am working on.
Could you help me how the Niggli ratio should be calculated?
Please let me know in details as well as an example.
During field work, i saw many quartz veins inside marble beds. The average thickness of them about (2 to 15 cm), and length abouth 1 to 6 meters that contained some sulfide grains such as chalcopyrite, Iron oxide, pyrite, malachite, and galena...etc (some of them during microscopic study). This field located in the north of Zagros suture zone.
This Field photo shows the alternating layers of Fuchsite Quartz and Barite formed during Archean period, in Dharwar craton. Any suggestion about the interpretation?
With Regards, Sagar
I got a sample of a nice looking blue rock (see photos attached), and I would like to know what rock is it.
This rock must be already known also commercially, because I recently saw a piece of this rock worked in the shape of a fruit (Pear, life size), decorated with a silver leaf.
It is not Lapis Lazuli (not the same colour, and it lacks the typical Pyrite granulation, even if a single small Pyrite crystal is visible). It is not Sodalite (not the same colour, and it lacks the typical white veining). It could be a Sulphur-poor variety of Hauynite of some sort, but which is it exactly? Where does it came from?
The spider diagrams of REE in plagiogranites does not have any Eu anomaly. How can I remove the effect of plagioclase to get the Eu anamoly in plagiogranite? Can anyone help me?
Does anyone have an idea about how do we know the partitioning coeffecient of Ti in rutile equilibrated with felsic melts? This is important for trace element modeling of felsic magma if rutile is stable in the magma source. I saw that Bedard (2006GCA) used a value of 45, but I am not sure if this value is appropriate. How was this determined? Is it too low? Because Ti is the constituent of rutile, obviously we cannot simply use the ratio of Ti in melts and Ti in rutile (0.6) if I understand correctly.
Thanks for your help!
I want to determination pressure of gabbro formation by Nimis and Taylor (2000) method, who can help me for doing the calculations?
Whether the partial melting of mantle lithosphere can directly produce andesitic melts? Who can provide me available references with repect to this process? Thanks.
I have some diabase samples (SiO2=47-53 wt. %, MgO=6-10 wt. % and TiO2=0.7-1.2 wt. %), which consist of mainly clinopyroxene and plagioclase. There is no olivine and orthopyroxene appeared in the thin section. How could I calculate the melting temperature and pressure of the diabase samples?
Thanks for your help!
With best regards
As we know niobium and tantalum considered as incompatible, high field strength elements and the overall abundances of them in the continental crust are relatively low ..
Is that related to their mobility and their geochemical behaviour into the aqueous fluids which generated by dehydration of the subducting oceanic crust ? and how does their high ionic potential value made them immobile or insoluble into magmatic fluids ?
Unfortunately, I can't understand their geochemical behavior into late stage magmatic melts .. so please, I need any researches or references about them ...
Best regards ...
I measured the nickel content in pentlandite in two rocks which are genetically linked (a sheared chromitite and a talc-carbonate-schist). There is a depletion of nickel in the pentlandites of the talc-carbonate-schist relative to the sheared chromitite. Is this a common phenomenon and is there literature about this topic and its p-T-conditions (alteration of pentlandite in ultramafic rocks)?
I am looking to expand from petrological perspective and learn a bit about the chemistry and physics with possible links and applications to geology/geoscience.
Advanced undergrad/postgrad level would be best.
So far I am familiar with the works of Nesse and Deer, Howie & Zussmann that I used for mineral identification in igneous petrology.
I'm doing a petrography study of granitoids and I suspect, based on optical properties, the presence of these two minerals in my thin sections. However, I don't have any certainty and I don't know how to distinguish between them since they have very similar optical properties. I would appreciate any tips.
In a geochemical book that mentions that sodic alkali basalts are relatively high TiO2 and in contrast potassic alkali basalts are characterized by low TiO2 content. I wonder which factors govern the content of TiO2 in basalts?
I found this texture, I have the impression that this ignimbrite was in contact with water. Is there any publication on vitreous ignimbrites ?.
the outcrop appears as a continuous mantle.
black is obsidian, and appears in spherical forms.
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,
The Laacher See complex plinian explosive volcanic eruption (12.9 ky BP, East Eifel Volcanic Field, Germany) appears to be unique in having erupted both representative portions of the zoned chamber magmatic liquids as well as representative cumulates from chamber roof, sides and floor in what seems to be very large amounts.
In most plinian eruptions, it is inferred that less than 1% of the magma chamber volume is erupted in the end.
However at Laacher See this proportion is inferred to be at least an order of magnitude larger; and indeed much larger estimâtes are even quoted in the literature on LSE.
The Laacher See Eruption has been extensively studied for over 40 years and such case studies seem to fulfill the dream of volcanologists to understand eruptions as well as that of igneous petrologists to constrain the relation between cumulate pile developpement (crystal mush) and the magmatic liquid line of descent.
I wonder if anyone has systematically ploughed the literature to assess how "unique" Laacher See complex plinian explosive eruptions may actually be ?
I would be grateful for any pointers or insights into this.
Happy holidays to everyone, and very best wishes for the New Year,
One has to consider plate tectonics, the age of the of the volcanic ash or indurated phase (e.g. tonsteins) and that of distant plutons,using a refined technique such as single-crystal zircon U-Pb dating, the microchemistry of glass inclusions in volcanic quartz, paleowinds, , and erosion of the the ultrasilicic volcanic ash, just to name several.
They have conspicuous concentration of vesicles in the center, irrespective of the orientation/inclination of the dyke.
Hello, everyone, I want to discuss with you to learn about if my following thoughts are suitable for deep research.
I want to compare the content of water, especially the structural water (OH), in nominally anhydrous minerals of granulite (Khondalite: gt-sill gneiss; mafic granulite: gt-px or two px granulite), S-type granulite, plagio-granite and then to discuss the influence of structural water in NAMs on decompression melting process of Khondalite and plagio-granite. As my previous study show that the S-type granite is formed by melting of granulite facies metasedimentary rocks and pagiogranite is generated by melting of basic rocks (most possibly the basic granulite or similar kinds of rocks), and there is concensus that granulite facies metamorphism occurrs at a dry condition and the water of protolith is dehydrated before the amphibolite facies metamorphism. So, I want to know if it is a good plan to learn about how the stuctural water content of minerals in khondalite work on the melting process to produce S-type granite, and similar to the plagiogranite which is produced by melting of basic rocks.
teaching earth & life sciences in a secondary school, I would like to find data about and to know how we explain size differences in colonnades diameter from basaltic (or rhyolitic) organs of distinct localizations?
Why such a long gap in the ages of same rock sample? Can anyone please suggest any good paper I can look into?
I'm looking for published data in order to determine some kind of average value for the "crust residence time" of MOR igneous products and compare them with intra-oceanic supra subduction zone igneous products (specially data obtained using Lu-Hf isotopic system).
I've been having difficulties in terms of identifying or being able to tell the difference between the paleosome and neosome visually. How do you tell if the paleosome exist in the migmatite rock by just looking at the hand specimen?
Spot data are needed to compile with ASTER for better identification of pegmatites in hardly accessible terrains. Are there interested collaborators?
Zircon Lu-Hf isotopic values are widely used to contribute to understanding of igneous petrogenesis. Epsilon Hf values of a suite of igneous rocks are often compared with those of different areas with different ages. Could anyone suggest a reference or references on zircon Lu-Hf values of Qiangtang terrane basement rocks?