Sedimentary Petrology - Science topic

To sum up:

The recommendations of Guenter Grundmann , Harald G. Dill and Patricia Roeser provide the best results for my question.

The British Geological Survey shares its deposites data on their homepage:

If you want to search for the quantitative mineralogical composition of rock use the phrase "X-ray Diffraction" in the text search and the rock you search for.

In the pangaea-data warehouse the mineral composition of rocks are sourced from publications. The search for locations is also possible. The raw data can be downloaded or can be viewed as html.

Ashok - H2O2 is used to remove organic matter from sediments - not carbonates. If you are trying to remove carbonates, but wish to leave any clay minerals unaffected, you should use a buffered sodium acetate/acetic acid solution (pH 5.3). If you aren't concerned about the clay minerals, dilute HCl would be fine. E-mail me if you would like the method.

Please compare the terminology of the terms "sedimentology" and "sedimentary petrology" given by the Glossary of Geology, Second Edition, Robert L. Bates and Julia A. Jackson, Editors (1980), and please decide for yourself what the similarities and differences are:

"sedimentology" (quotation): "The scientific study of sedimentary rocks and of the processes by which they were formed; the description, classification, origin, and interpretation of sediments. Sometimes miscalled 'sedimentation'."

"sedimentary petrology" (quotation): "The study of the composition, characteristics, and origin of sediments and sedimentary rocks. Often miscalled 'sedimentation'."

Best regards,

Guenter Grundmann

Dear Mr. Cevik,

there is simple recommendation I can give to you; determine everything in the field what you cannot determine in the laboratory, e.g., facial and structural architectural elements and save everything for the laboratory analyses such as the examination of thin section what you cannot determine with the hand lens or the unarmed eye. Then you become a very good geoscientists, because you are on the safe side and provided a good platform to create a model. If you have not done your work in the field properly the remaining downstream part does not deserve to be done at all. Your laboratory work cannot compensate for voids and deficiencies left after field work.

Kind regards H.G.Dill

Dear Mr Saber,

I agree with prof. Dill. These grains looks impurities released during the polishing of your thin sections. In your image 3-PPL, fibres from tissues used during the cleaning of your thins section are still attached to the surface. when you clean it it will disappear.

Dear Mr. Nejad,

your attempt to interpret the carbonate (micro) facies is very ambitious and is in my opinion not the correct way because the term facies is a far-reaching one to discuss the origin of a rock unit, in this case a sedimentary one where all available features of different scales need to be considered. The late Professor Walliser from Göttingen University once showed us a hand specimen and said: “ You should not create a new orogeny using only one hand specimen”. With kind regards H.G.Dill

Considering the limited variability of topaz in terms of major elements, studying trace elements, both of your heavy minerals and suspected source areas, might be the most fruitful approach. Perhaps cathodoluminescence imaging may also give some information (e.g. Agangi et al., 2016. Relation between cathodoluminescence and trace-element distribution of magmatic topaz from the Ary-Bulak massif, Russia. Mineralogical Magazine, 80(5): 881-899.

Dear Mr. Khan:

limestones are not that homogeneous as often people might think . I give you a rough scheme below:

aragonite

calcite Mg calcite (MgCO3 = 0 to 6 %; > 11 % at T values > 15°C and higher- up 40 %)

ferroan calcite (reducing environment)

dolomite ferroan dolomite/ ankerite (reducing environment, late diagenetic)

siderite (reducing environment, late diagenetic)

collophanite/ hydroxyl-apatite

clay minerals (e.g,. illite, smectite, sepiolite, glauconite...)

alkaline feldspar

siliceous compounds (derived from spicules, radiolarian tests, diatoms sulfate (gypsum, celestite)

chloride (halite)

They accommodate trace elements and REE in a different way . Therefore, without a proper knowledge of the mineral assemblage you hardly can attribute the various element contents to the different minerals. Unfortunately, the minerals are mostly members of the light mineral group.

Only some sulfates (celestite), phosphates and Fe-Mn-bearing carbonate minerals pertain to the "heavies". With this in mind it is difficult to design for you a family tree for the mineral processing. More information is necessary.

With kind regards

H.G.Dill

sajad

grain size , arrangement and cementation and matrix, diagnises , fossils.

Dear Ebrahim: your questions has been already answered by several colleagues, however I must point out two things. First, fossils can only give relative ages, I usually tell my students this funny analogy: Dinosaur bones don't have a tag attached saying "I was born 75 Ma ago!"... So to calibrate relative paleonthologigal ages, and also paleomagnetic time scales, one should have in the first case, a basin which, at the same time, is fossil-rich and has interestratified volcanic tuffs, lava flows or sills, and in the second case, a complete sequence of lavas showing several paleomagnetic inversions, such as MORB lavas or plateau basalts. These fossil+igneous basins could be rift basins, fore-arc or back-arc basins. The igneous tabular bodies present in them can be dated (usually in bentonites from weathered rhyolite tuffs, basalt flows, or diabase sills), and help to give upper and lower age limits to the fossil bearing strata linked to them. And second, that the so called absolute age of a rock has been substituted by a quite more realistic term as apparent age. This is because of what Asoori stated: rocks can be affected by many alteration processes, from metamorphism to hydrothermal alteration to weathering, that isotopic systems can be severely altered and give apparent ages which are not the real crystallisation or metamorphism ages. Systems with soluble cations, such Rb-Sr, and K, or with radiogenic gases, such as Ar, are easily modified by these secondary processes. Therefore the best methods used nowadays for primary crystallisation ages of igneous and metaigneous rocks are those effected in zircon crystals. Zircon, being a mineral resistant to secondary alterations, usually holds the true isotopic content reflecting the radioactive decay of U isotopes to Pb isotopes. It is a sort of miniature "time capsule", whose zoning can even record several successive orogenic or thermal events. Other methods of dating involving inmobile trace elements are: Sm-Nd, Lu-Hf, and Re-Os, applicable to specific rock types, and even to some Cu or Pt ores.

In Paleozoic granites of the Coastal Cordillera of Venezuela K-Ar method in biotite calculated 30 years ago gave quite "young" ages of 33 Ma; 20 years ago Rb-Sr isochrones gave quite "old" ages of about 404 Ma; but more recent U-Pb ages in zircon (LA-ICP-MS) gave even older ages, reaching to almost 500 Ma. It's a difference of almost 100 Ma, quite significant, indeed. The young Tertiary age has been interpreted as the orogenic uplift age, the oldest age, 495 Ma as the crystallisatin age of the plutons, so the 404 Ma Rb-Sr age was an apparent age, which really doesn't relate to either event! Therefore, hydrothermal and/or low metamorphic grade alterations have happened in these rocks disrupting somehow the Rb-Sr isotopic system. That's why absolute ages are no longer called such, they are apparent ages. With regards. Sebastian.

The rock appears to be a meta-sediment, probably a high grade quartzo-feldspathic schist or gneiss, derived from arkosic grits or sandy/siltstones.  If I am right and you examine it with a hand lens, you should be able to identify the following minerals: quartz and feldspars in the lighter layers and biotite mica with possible hornblende (amphibole) in the dark layers.  It is very similar to much of the Moine schists (Pre-cambrian) found in the NW Highlands of Scotland with which I am very familiar.  Hope this helps.

Dear Dr. Folly:

A distinctive reddish brown and white banded sedimentary rock from Kimberley of West Australia was called zebra rock, zebra stone or ribbon stone (Bevan 2002). It is composed of small particles of quartz and sericite, kaolinite and its polymorph, dickite, as well as alunite. Its color banding probably formed by the rhythmic precipitation of hematite- enriched bands during the alteration of the rock by percolating fluids. The zebra rock forms lenses extending for kilometers, within the Late Precambrian Johnny Cake

Shale. It is a fine-grained (anchimetamorphosed) sedimentary rock .

Bevan A.W.R. 2002 Rare Australian ornamental materials - zebra rock

an ornamental stone from the East Kimberley, Western Australia. Australian Mineralogist 21, 165-168.

Best regards

H.G.Dill

Nowhere, as far as I know. I was just making some general comments about Fe isotopes in case they would be helpful, and because I couldn't resist

Dear Dr. Mishra,

the presence of gypsum and pyrite may simply be predicted by the physical-chemical regime irrespective of the environments of deposition, be it lacustrine or any other freshwater environment.

1. The precipitation of gypsum and pyrite  is controlled by the availability of bivalent Fe and calcium in combination with sulfide or sulfate anions. They precipitate as the solubility product is exceeded.  Pyrite is pecipitated when the Eh is < 0 and gypsum needs an Eh > 0.

2. Yes, if you add, e.g. , Ca(OH)₂ to a sulfate-bearing system you will get CaSO₄ . 2 H₂O;  it does not depend upon the state of evaporation.

3. In many waste dumps at mining sites you can encounter  pyrite being converted into gypsum provided calcium ions are present. The climate needs not be aridic .

You can model it simply by using x-y plots ( x = pH, Y = Eh given in mvolt) with the soluble components being sulfur, iron and calcium in their ionic state.

Best regards

H.G.Dill

Dear Sandile,

First, intracrystalline deformation would be applicable on the constituent minerals of the rock and not on the whole rock itself. These deformation features are essentially solid state deformation feature, so if you see these on minerals then either 1) these minerals will belong to refractory part (which were deformed earlier) of the migmatite which escaped partial melting or, 2) the migmatite itself was deformed after migmatization. Therefore you should see the deformation features across different minerals lying in neighborhood, then only you become confirmed about the intracrystalline deformation and its implications. You may also see the variation in intracrystalline features when you approach from a zone of less partial melting to a zone of high partial melting ( such as SGR recrystallization to high T GBM recrystallization)

For detailed treatment regarding this issue you should consult books by Vernon, Blenkinshop or Passchier and Trouw (2005). Hope this helps.

Interesting photos and discussion.

Need to look at TS and CS in thin sections for texture and structure. as pointed out, the photos are insufficient to justify any concrete conclusion.

Possible options:

Hydrothermal vent deposits (observed in marine sediments deposited in proximity of volcanic vents where the gaseous fluids create tubular deposits of chert / carbonates with a concentric laminate pattern;

Ichnofossils - organic chert / calcite binding along tubular habitats of burrowing organisms - that leave behind such features

Simple fluid escape structures produced during lithification of silicic sediments under special conditions, where the fluids remain trapped in the lower strata and then are triggered into escape through tubular vents....(akin to mud-volcanoes)

....

I am assuming that since these are found in sedimentary rocks, other processes should not be brought into consideration, although even biogenic superficial weathering by soil-dwelling burrowers could also yield such features.

Dear Smaine,

This is a sort of "flat pebble conglomerate" common in the Lower Devonian from western Morocco into Algeria. These are thin beds that include large, hollow attachment structures of the crinoid Siphonocrinites. These attachment structures ("roots') appear either as large bulbous structures or are often broken up by wave activity into flat disk-like fragments and accompanying columnals from the stems. Wave imbrication stacks the fragments into an imbricated bioclastic conglomerate. These fragments are harder than such sulphates as barite. They are calcareous, but their composition is so dense that the fragments must be powdered (scratched) so that they can react actively with hydrochloric acid and produce bubbles. These are not Precambrian--Lower Paleozoic.

Best,

Ed L. 

Dear Haozheng,

I could not agree more with Esther. In fact there are a few papers out there which undertook this "exercise" and could help you about the applied methodology and expected concentration levels of "water" in different NAMs from granulites.

Németh, Bianka, et al. "Melting, fluid migration and fluid-rock interactions in the lower crust beneath the Bakony-Balaton Highland volcanic field: a silicate melt and fluid inclusion study." Mineralogy and Petrology 109.2 (2015): 217-234.

Zhang, Li, Junfeng Zhang, and Zhenmin Jin. "Metamorphic P–T–water conditions of the Yushugou granulites from the southeastern Tianshan orogen: Implications for Paleozoic accretionary orogeny." Gondwana Research (2015).

Yang, Xiao‐Zhi, et al. "Water contrast between Precambrian and Phanerozoic continental lower crust in eastern China." Journal of Geophysical Research: Solid Earth (1978–2012) 113.B8 (2008).

In spite of some unjustified criticism on the methodology I would still recommend you with confidence to use the unpolarized infrared methodology (see references below) (this would save you a lot of time and effort and would not worsen significantly the accuracy of your quantitative results), or in some cases it would make possible to have any quantitative data at all). There are only a few absorbance conditions which should be met for accurate results. Note, however, that this methodology is rather limited if you would like to constrain the crystallographic orientation of particular absorbers in minerals.

Kovács, István, et al. "Quantitative absorbance spectroscopy with unpolarized light: Part II. Experimental evaluation and development of a protocol for quantitative analysis of mineral IR spectra." American Mineralogist 93.5-6 (2008): 765-778.

Sambridge, Malcolm, et al. "Quantitative absorbance spectroscopy with unpolarized light: Part I. Physical and mathematical development." American Mineralogist 93.5-6 (2008): 751-764.

You can have access to the digital spectra of several NAMs from granulites in the PULI spectral database for free and you have the opportunity to share your own spectra with the wider community ( puli.mfgi. hu ).

I hope that this was a help and good luck with your research,

Cheers,

Istvan

Francis:

I thank you for your answers. Well, I am equally curious to find out the reasons for the apparent absence of chert in Holocene marine sediments. Incidently, I stumbled upon two references which needs to be shared and might help in understanding the issue involved:

1. Bohrmann et al. (1994): Pure siliceous ooze, a diagenetic environment for early chert formation, Geology, 22, 207-210. - The Formation of marine opal-CT nodules or layers as early diagenetic deposits has been documented only in Antarctic deep-sea sediments. This paper offers interesting insight.

2. Meister et al. (2014): Early diagenetic Quartz formation at a deep Iron oxidation front in the Eastern Equatorial Pacific - A modern analogue for banded Iron/chert formations? Geochemica et Cosmochimica Acta, 137, 188-207. This paper (ODP site 1226) convincingly attempts to explain as to why early diagenetic microcrystalline chert only occurs sporadically in modern sediments.

More occurrences from around the world with fresh insights may kindly be brought to our notice.

Best

Syed

Peraluminous granites are probably not the most prospective for REE exploration. By the way, it is a bit unusual that you mention sphene and alllanite in the supposedly peraluminous granite; both minerals are calcium-bearing, whereas peraluminous granites typically have a deficiency of calcium (hence their peraluminosity). So those Ca-bearing minerals may be more likely be associated with the mingled mafic magma than with the peraluminous granite itself.

Dear Mr. Xu,

the answer is yes. Amphibole and pyroxen accommodate in their crystal lattice bivalent Fe which as being exposed to oxygen more or less rapidly converts  into trivalent iron which shows up again as goethite or hematite dependant upon the degree of hydration. I attached a chart showing the realtive stability of heavy minerals against weathering. As you might conclude from this order of stability, pyroxene and olivine are the most vulnerable Fe-Mg-bearing heavy minerals, Amphibole is more stable, whereas zircon, tourmaline and rutile belong to the most resistante heavy minerals. Fe-bearing pyroxene and amphibole often end up as dioctahedral smectite such as nontronite which also contains trivalent Fe. Pyroxene and amphibole also swiftly decompose in sandstones upon deep burial during diagenesis. Amphibole is in this case more resistant, while pyroxene persists at its very low level in this stability charts.

I hope it will help you. Should you have further questions I refer you to my papers on heavy minerals amenable for download from the RG server.

Best regards

H.G.Dill

Structures shaped like chevrons, or series of chevrons? Individual chevrons may include various sole marks described by Reineck & Singh in 'Depositional Sedimentary Environments' (e.g., fig. 102 in the 1975 edition). Series of chevrons may be of biogenic origin (trace fossils such as Protovirgularia) or inorganic origin (chevron marks; Reineck & Singh, 1975, fig. 112).

Dear Longgang,

Please consider precipitation of "marine evaporites". You can read precipitadion conditions of evaporites that occured as a consequence of "MESSINIAN SALINITY CRISIS". There is many publication in the web.

Best wishes,

Erhan

The best way to obtain a numerical age for a sedimentary rock – other than through comparison of fossil content or magnetopolarity reversals with the geological timescale – is through the direct dating of volcanic ash layers (U-Pb and Ar-Ar techniques on mineral separates). The main difficulties with this approach relate to the mixing of grains of different age and significance, and alteration of the dated minerals. An approach that works really well in marine deposits of Oligocene-Miocene age is to measure Sr isotope ratios in microfossils and macrofossils. The seawater ratio is well established for that interval, and more or less linear. Glauconite dating is mostly a mess. Poor resolution.

Dear Mr. Oluwajana,

I can only support the previous answers to the question which were more a sort of a soft claim of getting more information about the environment of deposition and of the positioning of the image.

It is a clayish matrix and the concentric rings show a slight change in color caused by a variation of the valence state of Fe, due to oxidation. The diameter of the tubular structures lies between that of a tree trunk and a simple root fragment. They are well oriented and as such they might fall into the size range covered by the above floral remains.

Another feature very common in environments abundant in bituminous material belongs to the natural gas seepages which are known from many places such as the Eocene beds of Pobitite Kamani, Bulgaria.

So far there is a lot of uncertainty in my answer due to the lack of information on the internal texture of the tubular or ring-like structures and the host environment. I attach two papers of mine, one from a true coal-bearing environment the other from a transitional environment of the Nepalese Kathmandu Lake, where lignites and bituminous sedimentary rocks occur side-by-side nearshre. Maybe both papers help you to restructure your question and to single out the features you find of assistance in the interpretation of the host environment and the physical-chemical regime.

At the current stage I do not dare to give you a clearer answer.

Best regards

H.G.Dill

Not need for further explanation, your question has been answered through the discussion thanks to the input of all the participants. By the way, that figure is from one of my papers (Fig 3f): Campos Alvarez and Roser 2007. Geochemistry of black shales from the Lower Cretaceous Paja Formation, Eastern Cordillera, Colombia: Source weathering, provenance, and tectonic setting, Journal of South American Earth Sciences 23, 271–289, and simply reflects the abundance of clay minerals is indicated by low K2O/Al2O3 ratios (<0.3), similar with the ranges of clays (Fig. 3f) but significantly different from the higher ratios (0.3–0.9) typical of feldspars.........just keep it simple

In rock or any crystalline form it is good if XRD or XRF to use since it is difficult to extract NO3 from the rocks

Thanks Kenneth

What about if use IR analysis?