Sedimentary Geochemistry - Science topic

Dear Colleague,

It is very possible to use DDR 3 for manual acquisition of 3D resistivity data but however requires intensive labour, prolonged duration on the field, more financial expenditure as the survey may spill into the following day if not completed.

The smartest way to embark on the acquisition, is by designing a spreadsheet that accepts all field parameters and automatically computes the apparent resistivity for effective monitoring of data trend.

It therefore advisable to input all recordings on a smart phone or tab when using DDR 3 for 3D acquisition.

Regards,

Alaka.

The calculation you are doing is to account for (exclude) the presence of apatite (Ca₅[PO₄]₃(OH, F, Cl), in which (ideally) there are 5 moles of CaO and 1.5 moles of P₂O₅. So, for every mole of P₂O₅ you need to subtract 3.33 (10/3) moles of CaO assuming it is all in apatite, then see how much CaO is left over.

However, depending on the rock type, not all the P₂O₅ (or indeed any of it) needs to be in apatite. For example, in metapelites, it might be in monazite. You should also check that you have converted your bulk compositions to molecular rather than weight percent values. Lastly, all analyses are associated with uncertainties that need to be accounted for.

What negative values are you getting?

Good luck.

Dear Mr. Daoud,

just this type was investigated in the cited paper:

DILL, H.G., BERNER, Z., KAUFHOLD, S., WEBER, B. and METZ, U. (2013) Facies-related baryte mineralization bearing Cu-Zn sulfides in Miocene estuarine deposits of the upper Rhein Graben (Wetterau, Central Germany).- Sedimentary Geology, 296: 55-71.

Abstract: Abstract

Baryte with or without base metal sulfides is quite common in sediments deposited in open marine environments or in continental sedimentary basins. Its precipitation is caused by hydrothermal processes, related to diagenesis, and frequently mediated by biogenic processes. The current study is focused on siliciclastic sandstones of Miocene (Aquitanian) age in an estuarine environment in the Wetterau region of the Rhein Graben, central Germany. In the estuarine environment only the central basin and the landward delta are host to a diagenetic and subsequent hydrothermal mineralization.

Diagenesis took place under near-ambient ( T ≈ 25°C) conditions and resulted in strong pyritization (-0.75 <Eh < +0.25, pH >5) in the central basin. Diagenesis is more landward represented by a pervasive silicification (pH < 12) in deltaic sandstones.

Epigenetic mineralization (100°-130°C) with pyrite in the central basins was succeeded by Cu-Zn-(Sb) minerals (0.75 < Eh < 0 / 5 < pH < 11), silicification and kaolinisation (2< pH < 9.5) and eventually by the formation of gibbsite (3 <pH<8). At the transition from the delta to the estuarine funnel, baryte is of very widespread occurrence. Its variegated texture and crystal morphology allow for a precise determination of the hydraulic system as marine phreatic, freshwater phreatic, and freshwater vadose. The narrow size of the rift graben and its sealing against the open sea fostered concentration of Ba and enhanced the redox processes. Hypogene brines along with Miocene volcanic activity provided the metals, and marine ingressions in this transitional environment supplied the sulfur. Sulfides were concentrated in the finer-grained rocks because of their enrichment in organic material, while sulfates accumulated in the more permeable coarser sandstones.

H.G.D.

Aie...

Not so easy, Sr is mostly associated to Marine carbonate, thus in lake terrigenious carbonate and not in lake carbonate productivity. By this way Ca/Sr could be used as in lake carbonate productivity.

If you do not have terrigenious carbonate you can try estimate the Sr in silicate during a period oh high terrigenious inputs: flood deposit or late glacial period (all Sr = silicate end member). But if you have different terrigenious sources or terrigenious carbonate for me it is impossible with just these data....

Best regards

Pierre

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.

Dear Mr. Morad,

Unless you have carried out a geological survey and studied the mineralogical association of your rocks the chemical studies and the use of any index based upon chemical data is meaningless. It is a repetive critics of mine.

It is good for riding the “paper-tiger” but in practice these figures are of no use. Because what it is all about, is the futile attempt to circumnavigate experience and knowledge in geology and mineralogy. To gather experience needs time and to pile up knowledge even more in combination with a series of physical and mental endowments.

We cannot delegate geosciences to the technicians in the chemical lab.

Sorry for this harsh critics which is a general statement rather a reference to your question.

Sincerely yours

Harald G. Dill

Dear Mr. Pratihari,

there is only one way to come close to a solution in provenance analysis.

1. Given there is enough information available on the geological setting investigate the mineralogical assemblage which is based upon heavy , light minerals and lithoclasts

2. Conduct further studies either based upon whole rock chemistry of major and/or trace elements or mineral chemistry, even better.

If you put the cart before the horse it is poking around in the fog, or to be more precise wasted time and wasted money.

With kind regards

H.G.Dill

I agree with Ramon and Ahmed. The conditions Ahmed describes occur less disturbed along passive margins such as the Gulf of Mexico, the Santos and Campos Basins offshore Brazil, the offshore basins of West Africa, and many others. In tectonically active margins, the sedimentary record can be disturbed by earthquakes, overturned in folding events caused by compression, strike-slip faulting, or active volcanoes.

Hi Jorge

I agree it's certainly possible. However, since XRF only detects the Fe content not the O content, the meaured Fe content will not change as a result of its oxidation state: this was the point I was aiming to make.

Kindest Regards

Paul.

CaO* is the content of CaO incorporated in silicate fraction. McLennan (1993) proposed an indirect method for quantifying CaO content of silicate fraction assuming reasonable values of Ca/Na ratios of silicate material. Procedure for quantification of CaO content (CaO*) of silicate fraction involves subtraction of molar proportion of P2O5 from the molar proportion of total CaO. After subtraction, if the “remaining number of moles” is found to be less than the molar proportion of Na2O, then the “remaining number of moles” is considered as the molar proportion of CaO of silicate fraction. If the “remaining number of moles” is greater than the molar proportion of Na2O, then the molar proportion of Na2O is considered as the molar proportion of CaO of silicate fraction (CaO*).

Dear Osama,

Thank you for your share Osama Rahil Shaltami .

This publication looks very helpful. but I can not download it now, I will download and read it next Monday.

Thank you for your help.

Best regards

Bangjun

Dear Sir

I think the links below will benefit you in your search

Best Regards

Dear Sir

I think the links below will benefit you in your search

Best Regards

Dear Mr. Mahboubi Chikh Younes,

ankerite [Ca(Fe⁺⁺,Mg,Mn)(CO₃)₂] , an Fe- and Mn-bearing dolomite, is a typical marker mineral like siderite or Fe-bearing calcite, all of which accommodate bivalent iron in their lattice given anoxic conditions exist (may also be present in an oxidizing regime if the pH value allows it). Trivalent iron present under oxidizing conditions cannot enter the structure of these carbonate minerals and occurs, e.g., as “limonite” or hematite along cleavage planes. For a detailed description of the redox condition in an x-y plot displaying the pH and Eh (mV) you need to know the soluble components such as total sulfur or carbon dioxide activities in the aquatic system as well as the temperature of formation. For a detailed information about this issue consult the classical studies of Garrels & Christ 1965, where you will find the basics good for learning.

With kind regards

H.G.Dill

@Jean Daniel stanley sir I have followed your formula also, but where their is no mangrove. Is it right practice to calculate the subsidence?

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

The geochemical/elemental data of sediments with mixed, multimodal, poorly sorted texture/high sand content may mislead in interpreting the provenance and chemical weathering. For chemical weathering, the commonly used proxies are CIA, PIA, CIW etc. In the original paper which has proposed the CIA, the originators of this measure (Nesbitt and Young, 1982) have used clay (lutite) fraction to avoid the effect of size-segregation. The weathering product is a reflection of breakdown of vulnerable minerals for alteration such as feldspars. The formula is a ratio of alumina and alkalies, both of which are not abundant in minerals such as quartz which may dominate the sand-sized material.

For provenance too, commonly used geochemical discrimination diagrams/ratios may not be suitable for sediments with varying texture. Recently, a paper on estuarine sediments has shown the sediments are products of basic rocks from the elemental composition of bulk analyses data (not considering the textural variation). We have recently performed geochemical analyses of both bulk sediments and the clay-sized fraction from the same estuarine area. While the bulk sediments have shown a basic to intermediate composition, the clay-sized fraction has shown felsic source composition. The problems associated with size sorting would be more common when we deal with riverine, estuarine and coastal areas which will have energy conditions at some places. It may not be severe when we deal with deep-sea clays.

Ideally, clay-sized fraction would be suitable for interpreting provenance and chemical weathering unless the intention is to determining the provenance of sand-sized fraction.

heavy and clay minerals are good indicators...

For example

Chemical analysis of sediment and ratios like Ca/Fe, Sr values, K/Al will give provinances

In addtion to the answers already given, diagenesis of carbonate in bio-apaptite will cause isotopic fractionation.  The direction of which depends on the nature of the process.  Long-term exposure to water (immersion) will shift carbonate d18O towards water d18O. Processes that produce CO2 as end-product will typically result in the remaining carbonate to become heavier in 18O.

The phosphate fraction of bio-apatite is virtually impervious to diagenesis which is why archaelogists and paleoecologist tend to prefer phosphate d18O over carbonate d18O.

Working on the basis of bio-apatite phosphate d18O values to be "true" one can use the correlation equations published by Iacumen et al. (1996) and Chenery et al. (2012) for bone and teeth respectively to check if corresponding carbonate d18O values are artefact free.

Dear colleague:

There is a wide range of marks and traces in the field of inorganic and organic sedimentology which have some implications on the paleobathymetry of sedimentary strata. The same holds true for the floral and faunal remains in paleontology. There are much more publications, items and species of assistance to address this issue than room available in this Q&A process on Researchgate.

I wish you much success

H.G.Dill

Apatite is a common U-bearing accessory mineral with a U-Pb closure temperature of ∼500°C, making U-Pb dating of apatite a potentially valuable thermochronometer.

However, its low U concentration and tendency to incorporate common lead has limited widespread application to destructive isotope dilution methods, Laser ablation–multicollector–ICPMS can be used to overcome the limitations.

Apatite is also used for  Fission-track dating, for determining low-temperature thermal events, typically 0.1 Ma to 2000 Ma. Apatite, contain enough uranium to be useful in dating samples of relatively young age (Mesozoic and Cenozoic) and is mostly used for this technique.

If you know the age of the granitic rocks Proterozoic/ Archean...with reference to what new age/ data you want to do apatite dating.

Please have clarity what you want actually from your study before you proceed.

Thank you Roberto. I have photomicrographs from the SEM for the brachiopod shells which mostly show good preservation of the shell ultrastructure. I guess making thin sections for the bulk rocks is the only thing lacking now. Thanks once again.

Some more details would be good (e.g. what environment, do the isotopes increase or decrease down the profile etc.). If you post a figure with the down core d1C values that might help the community interperate your results. A few suggested reasons are:

If you see a trend of isotopic enrichment or depletion with depth in could indicate a changing organic matter source over time (e.g. shift from C4 to C3 vegetation type or vice versa) or

shifting isotope values with decomposition e.g. https://www.researchgate.net/publication/277132253_Distinct_fungal_and_bacterial_d13C_signatures_as_potential_drivers_of_increasing_d13C_of_soil_organic_matter_with_depth

All the best

Damien

The age of fresh, unweathered zircons by radiometeric dating will only provide the date the crystal was formed. However by studying the colour and other physical properties of a reasonably large number of zircons in a sedimentary rock such as till, the source of the sediment can often be inferred. To do this, it is essential to know the properties of the zircons that may be present in all the rocks over which the sediment may have passed.

Stuart.

Here goes some relevant work..

Abstract; To determine the extent of metal association in natural iron oxides, a combination of XRD and chemical selective dissolution techniques was applied to four samples from laterites developed on peridotites in East Africa. The reagents used were dithionite-citrate-bicarbonate (DCB), citrate-bicarbonate (CB), hydroxylamine hydrochloride (HH), and oxalic acid-oxalate (Tamm). From the results obtained, it appears that: (1) the difference DCB minus CB is a better estimator of the metal fraction in Fe oxides than the difference DCB minus oxalic acid-oxalate, especially in presence of gibbsite; (2) the use of HH allows to be distinguished the specific contribution of Mn oxide; and (3) geochemical models for goethite must provide for the existence of ternary solid solutions (Fe, Al, Cr).With regard to the geochemical properties of the elements, it can be concluded that: (1) Cr substitutes for Fe in the same proportions in goethite, hematite, and maghemite; (2) in contrast, A1 substitutes largely for Fe in goethite, little in hematite, and not at all in maghemite; (3) Mn substitutes partly for Fe, but forms discrete phases when total Mn content is high; (4) Ti substitutes for Fe in hematite, but not in goethite; (5) the major Cu-bearing phase is a spinel; and (6) Ni is closely associated with goethite and not with Mn oxides and spinel.

Abstract—Geochemical and mineralogical investigations, including measurements of major and trace elements, Sr isotope ratios, and 238U-234U-230Th activity ratios, were made on an old African laterite to reconstruct its formation steps and assess recent chemical mobilization. The present data support a scenario of discontinuous formation for the laterite, with different bedrock weathering conditions during the formation of each unit, rather than a scenario of continuous formation. Absolute accumulation of Fe, U, and lanthanides in the uppermost ferruginous unit suggests an autochthonous origin of this iron cap by leaching of an older overlying profile. Present chemical distributions of lanthanides, as well as of Rb, K, Ba, and Sr, within the profile cannot be linked to the mineralogical distribution of both relictual primary and authigenic secondary phases.  Complementary lanthanide patterns indicate that these elements were primarily accumulated in the uppermost ferruginous unit before further remobilization and accumulation in the underlying horizons. These redistribution processes may be related to the chemical instability of the ferruginous cap. The 238U-234U-230Th disequilibria indicate that recent U mobilization occurs in the whole profile and that, as for lanthanides, there is a vertical redistribution of U from the uppermost ferruginous unit to the underlying horizons. Moreover, these data show that both U losses and gains exist at each level of the profile. A simple modeling of this double U mobilization process is proposed to interpret the 238U-234U-230Th data. Differences in the mobilization and fractionation intensities of the U input and removal processes can account for the two evolution trends, whichdistinguish the ferruginous unit from the underlying ones. Furthermore, on the basis of this modeling, the profile appears to be in a transient state because of recent changes in the U mobilization conditions, whichcould correspond to major Pleistocene climatic variations. PDF enclosed for further reading...

It is clear that a job of cleaning and using the 3D scanning technique would help a lot. However, looking briefly and apparently the first plates appear to be benthic foraminifera of the genus Textularia; The third plate reminds me of benthic foraminifera of the genus Ammonia and the last plate really needs to be more worked on in the cleaning and for me they are difficult to be identified.

Dear Prakash,

Your photographs clearly show alluvial and/or mixed alluvial-colluvial earth materials, which are more or less weathered with elements of more (the most ferruginized) or less weathered parent rocks (among which sandstones, and limestones ??). What you call nodules and/or concretions are such ferruginized parent rock elements, which have been eroded/transported/deposited rather than typical ferricretes or Fe nodules/concretions previously formed in a lateritic profile. For me, the apparent ferruginization of some elements is rather indicative of sedimentary processes than classical lateritization. However, on some cuts and sections, recent lateritic weathering of the alluvial deposit can be observed and interpreted as such. I cannot tell more based on the provided photographs. The XRD and ICPMS analyses will document precisely the composition and potential origin/source of this alluvial deposits. With my best Regards, and thank you. Anicet B.

Hello Dr Latha,

I presume from what you described that you have a U-Pb TIMS lab capable of low blank (sub pg common Pb), single zircon work and supported by decent mineral separation facilities and zircon prep.  The issue to consider with fracturing and deformation of the host rocks is mainly lead loss from zircon surface domains and your ability to remove those by say chemical abrasion, which post dates my experience with air abrasion.   An additional problem in your case, distinguishing the ages of basement and intrusive granitoids, is inheritance.   I cannot say much about the Rb-Sr systematics from limited experience except to say I have seem protolith ages preserved in domains within granulite facies gneisses.

Where I would start is to classify the granitoids by composition and in particular I vs S type.  With I type you might also find titantite, which would help confirm lower end ages and with S type, monazite or maybe xenotime, also useful for direct igneous crystallization ages, metamorphic ages and major hydrothermal events.  S type granitoids are more susceptible to zircon inheritance although this has to be suspected in any case.   I would also look out for clastic sedimentary rocks in the basement as sources of older detrital zircon and the proximity of both basement and later granitoids. Cathodoluminescence  may help with 

You mentioned that the zircons are very scarce so that is another reason to look for monazite or titanite.  However, you should also check your mineral separation facilities if you suspect that you are getting low recoveries of zircon.  Smaller zircons can be washed out in the light fraction on a Wilfley table if it is not operating at the right speed.  Or you might be losing them in inefficient magnetite separations if you are dealing with e.g. gabbros and have a lot of magnetite or a propylitically altered rock and have a lot of pyrite.   On the other hand a scarcity of zircons is not a reason to consider the rocks unsuitable for U-Pb dating.  You may only need a few zircon grains.

The problem in your situation also depends on the age, and age difference of the basement and intrusive, mineralized granitoids and therefore the precision you need to distinguish them.  If they are both Archean you may be fine with just the zircons so long as you do not have significant lead loss events.  With younger .e.g. Mesozoic granitoids I would back up the zircons with monazite or titanite.  

As for leaf litter fall in tropical forest of North East India, my paper might give you an idea. Please go through it "Impact of Shifting Cultivation on Litter Accumulation and Properties of Jhum Soils of North East India"

in a simple manner, the chemical diagenesis needs water to reacts with the rock and sediments.

this is which called water/rock interaction (dissolution - precipitation - replacement)

these processes are stopped in two cases:

1. no water present in the system ( assumption  case)

2. the water and rock are in equilibrium (nearly impossible case) and fixing all environmental variables.

then, the stop of chemical diagenesis is named when the chemical diagenesis is minimized to the lower level.

I thick that this classification will help you 

HCl is by far the easiest method if this acid does not alter other mineral phases such as clay minerals. You can also try to use warm formic, acetic or citric acid I presume.  

Thank you so much for your kind words.

Please send me your e-mail so I can send you that paper. There is an excellent paper by MA Mahar et al, 2016, Timing and origin of migmatitic gneisses in south Karakoram...J Asian Earth Sci 120, 1-16. 

Three contributions on Shigar valley by Carl Hanson are:

Hanson, C.R., 1986. Bed rock geology of the Shigar valley area, Skardu, Northern Pakistan. M.S. Thesis, Dartmouth College, Hanover, New Hampshir, 124p (I gave a copy of it to Peshawar Cntre)

Hanson, C.R. & Lyons, J.B., 1986. Bedrock geology of the Shigar Valley area, Skardu, Northeast Pakistan. Abstracts with Programs, Geological Society of America 18(6), p. 627.

 Hanson, C.R., 1989. The northern suture in Shigar valley, Baltistan, northern Pakistan. In: Malinconico, L.L. & Lillie, R.J. (eds.), Tectonics of the Western Himalaya. Geological Society of America, Special Paper 232, 203-216. (I have a copy of this volume).

Best wishes, Qasim

Dear Mr. Chai,

for paragneisses derived from psammo-pelitic rocks the following parameters and ratios are recommended: K/Rb approx. 250, Ti > 0.5 %, enriched in Al, Cr, Ti, Ni, Co (> 10 ppm

for paraamphibolites (marl) the following data are known:  low contents of Cr, Ni, Co, V, Ti, enriched in B, Li, Rb, Cs, relative to orthoamphibolite. Sr/Ba < 1, Cr/Ni < 1, Mg-V, Cr-V positively correlated Ti-V, Cr-Cu is negatively correlated  up to o.5 % C.

paraultrabasic rocks (evaporitic) are enriched in Be, Ge, B.

Maybe it gives you some ideas for the parent environment of your metasediments.

Best regards

H.G.Dill

Dear Simona,

Thanks for your sending information.

Youngmin

Thanks for all your answers and suggestions. I really agree that the sulfur signals of pyrite are controlled by multi-processes. Here I would like to attach our fresh results from the inner-shelf of the East China Sea (36 m water depth).

In spite of consistent contents of the organic carbon (TOC), we find that the sulfur contents (TS) and isotopic values (δ34S) show significant variability from the core bottom to top. In general, when sedimentation rates are high (i.e., U2, U4 U6), the TS increase combined with high δ34S values. In detail, the U2 with the extremely high δ34S values (as high as 75‰) is different from the U4 (near the sulfate values in present seawater 20‰). Could these both unites can be explained by high rates of bacterial sulfate reduction (BSR, related to sedimentation rates) in a closed system (BSR)? In contrast, do these lighter pyrites in the U3 and U5 relate to BSR in the open system?

Dear Mr. Sobolev:

Chakhmouradian (2006) recorded it from carbonatites, where its crystallization is controlled by other Ti, Nb, and Zr minerals, such as perovskite, pyrochlore, ilmenite, baddeleyite, and zircon. It is present in the Chilwa Alkaline Province (Malawi) and it is common in pegmatites as demonstrated by Szełęg and Škoda  (2008) from the Y, REE-rich Skalna Brama pegmatite near Szklarska Poręba. Maybe this paper comes closer to your issue: Zaccarini , F., S tumpf l, E .F. & Garuti, G . (2004): Zirconolite and Zr–Th–U minerals in chromitites of the Finero complex, Western Alps, Italy: evidence for carbonatite-type metasomatism in a subcontinental mantle plume. Can. Mineral. 42, 1825-1845.

Best regards

H.G.Dill

The described conditions (relatively high TOC, very low S1, low S2 and S3) indicate spent and stripped source rock, i.e. a rock that originally was very rich in TOC, but excessive maturity generated all the hydrocarbons that could be generated from that rock, and such hydrocarbons left the rock altogether, leaving behind only residual, cocked carbon, unable to generate more hydrocarbons but still counting as Organic Carbon. Such rocks would be black, but are not source rock. They are former source rock. You could check the rock maturity indicators (vitrinite reflectance for post-Devonian rocks, other thermal maturity indexes including illite crystallinity).

See for example http://geomuseu.ist.utl.pt/IGR2012/Petroleum%20Geochemistry%20/basic_petroleum.pdf

Der Asoori: Not much to add to Roberto's answer, perhaps that the deep chemical weathering at world famous Tsumeb mine occurs as deep as 1,5 km below the surface, since the host limestone was deeply faulted and the fault plane was permeable enough to allow meteoric water, laden with oxygen and CO2 (among other anions...), to create outstanding oxydation zones, which produced incredibly beatiful specimens of Cu-Zn-Pb minerals of the carbonate, arsenate and phospate classes, such as azurite, cerussite, malachite, rodochrosite, smithsonite, and hundreds. Also have to be considered the processes which occur during diagenesis, some of them quite similar to those ocurring during weathering, and also dependant on the redox chemical conditions of the altering fluids. Regards. Sebastian.

Thank you Dr. Vafadar.

Dear Teddy,

              Best thing you can do just sieve it through different mesh size. You can get the different fraction of sand, silt and clay. Measured it  and you will get suspended sediment load (gm/liter) in the water also. If you want to study the other properties in details then you go for SEM. 

Regards

Dear Dr. Liu,

it seems to be a type of C-bearing material which reflects the morphology of body fossils and trace fossils. As I do not know any values of reflectivity I can give only a vague explanation as to the state of coalification which in my opinion lies between the low volatile bituminous and anthracite state. It is mere speculation to say that it is kataimpsonite, a high-grade metamorphic bitumen (?). What is the diagenesis or regional metamorphism of the rocks in question like ?

Best regards

H.G.Dill

Dear Mr. Tripathi,

why do you take refuge to sulfur isotopes ? First make an attempt using geological methods such as sedimentological ones, than go into sedimentary-mineralogy (heavy and light minerals, phyllosilicates). Also the major and minor elements offer a lot in terms of recognition of the paleo-environment. There exists a wealth of papers. Do not saddle the horse from the tail and follow straightforward the common way of geoscientific work.

This is based on almost 40 years working in the geoscientific business.

H.G.Dill

Suman:

Have a look at this link for an elegant example from Miliolitic Limestone of Saurashtra, India:

Best

Syed

Nice thin section photo!

There are two aspects of maturity in sandstones.  One is textural maturity, which is indicated by well sorted, well rounded sand grains.  The other is compositional maturity, which is indicated by a high proportion of quartz and a stable heavy mineral suite dominated by the likes of zircon, magnetitie, etc.  Most of the time, textural and compositional maturity go hand in hand, but not always.  The quartz grains in your thin section are pretty angular still, so this rock is definitely not texturally mature.

Yes, I think that even though this proportion of cement is high, cement is diagenetic, and not part of Dott's classification.  This would be classified as a ferruginous quartz arenite to me, but in the more detailed description (which you have done very well) you would point out the high amount of cement.

I am working on the Jacobsville Sandstone, which is Neoproterozoic in age and found in the Lake Superior area.  In places it is very similar in texture and composition as yours.  My work has been on its age, provenance, and tectonic significance, but folks before me have worked on the sedimentological characteristics.  There are a couple of papers that I have up on ResearchGate that may interest you.  Lots of references in there on the sedimentology.  There is a very high proportion of hematite cement in places and it is difficult to tell whether it is matrix i.e depositional (some is definitely detrital and eroded from the underlying BIFs) or cement i.e.diagenetic in places.  There are some folks who are working on isotopically dating the hematite.  If you like I can send you some hand specimines or heavy mineral splits, just let me know.

Good luck,

Dear Dr Flemming.

Maybe the data set  below can be useful.

Best regards,

Alexandre Cabral

Hi there, it can be useful for you:

First crush the black shale.  Sieve it to obtain different size fractions.  Wash them with distilled water to remove all the powder and muck.  Wash with acetone (to prevent oxidation) and dry.  Examine under the binocular microscope to know  which size fraction contains the maximum number of pyrite grains. In fact,  before doing all this, get one polished thin section made and examine under reflected pol.light to obtain the size of the pyrite grains so that straight away you can crush the sample to that size by using the necessary sieves and wash that particular size fraction.  Since you want to separate physically, separate them by hand piking with a needle dipped in acetone/xylene making use of binocular microscope. Or else, you can also use Frantz Isodynamic separator.  Even you can try hand magnet as well -as sometimes pyrite is also magnetic.   By the by all this information (even better information / guidance)- I feel, you should be able to get from the staff members in your Department.  All the best. K.N.RAO

PS:- The black shale's black colour may be due to the presence of pyrite -which means it ( pyrite) is altered and you may have to collect considerable amount to obtain unaltered pure fraction required.  It all depends on what for you want the pyrite grains. Is it for sulphur isotope studies?

The subduction-related fluid are riched by LIL elements (Sr, Pb, Rb, K). If the basalts are high-potassium, then the magma protholite contains phlogopite. A positive correlation of K/La to K in basalts is an indicator of the presence of phlogopite and water in the mantle. Restitic association with melting hydrated mantle comprises a titanium-containing phase (e.g., rutile) - Ta-Nb minimum in melts.

Bencaabane:

You would find this link useful:

Best

Syed

A mass spectrometer is normally front ended with an elemental analyzer. this means that you should get values of TN as well as d15N. So check your d15N output and you will notice that there should also be N (TN) values.

I forgot to mention, organics can sometimes be attached or even grow into the bedrock, boulders, cobbles, gravel, etc.  This material may have roots embedded into the rock fractures, or on other instances need to be scrubbed to remove.  This may or may not be an issue with your circumstances.

The attached images No 1-3 show a polished thin section of a biotite-muscovite gneiss, in which the mica flakes are oriented more or less perpendicular to the ground surface. Here the quality of the surface is largely free from scratches. Image 4 shows the mica flakes more or less parallel to the polished surface. Here you can see numerous cracks, holes and scratches which damage the surface.

With the following steps, you can (avoid cracks, holes and scatches) create a dispersed mica sample that meets the requirements of the electron microprobe analysis.

1) An acrylglass ring of 20 mm diameter, about 2 mm thickness and 5 to 10 mm height is ground plane-parallel (fig 5).

2) One of the ground surfaces is covered with a double-sided adhesive tape, the inner surface is to be removed.

3) A commercially available aluminum foil is fixed twice on a flat surface.

4) The one side covered with the tape will now be firmly pressed onto the aluminum foil.

5) The interior of the ring will be filled to just below the rim with resin.

6) A mixture of quartz grains and mica grains, which have about the same diameter now carefully scattered onto the resin surface.

7) The quartz and mica will sink down onto the aluminum foil surface due to the higher weight. Possible air bubbles must be removed carefully with a fine brush.

8) After curing, the aluminum foil can be drawn off and the mount can be sanded and polished.

The embedded quartz grains prevent flattening and stacking of the mica flakes.

Try it! It works!

Best regards,

Guenter Grundmann

That is possible, but a more important and major source in many cases is probably apatite in sediments including phosphate beds.

I Would talk to geologist, well driller and logger who are used to aerial cable systems (skyline or high lead).  The logger is to rig up cable system to pile drive or use suspended heavy log for weight to push in core, and extract pipe with core using cable and connections.  The geologist and well driller for more ideas, such as on whether coring needs to be rotated periodically to break bond with soil, core.  They should know the feasibility of this.  Coring at an angle from stable bank may also be considered with core sampler.  They should know the feasibility of that option.  

please go through the article "Sinha et al., A leading mode of Indian summer monsoon precipitation varibility during the last millennium" GRL, 38, (2011)

Can you give more information by email please.

Martin feely

While it is generally true that both porosity and permeability decreases with depth you can expect abrupt permeability changes with depth.  This is a function of stratigraphy, the composition of sedimentary layers and diagenesis.  Even the same stratigraphic layer, roughly at the same depth may show significant lateral permeability changes due to lateral facies and diagenesis changes.  Sorry, no simple answer.

Regards, Volker

Dear Ramzi,

If you can access the journal, you can find a (rather old) worked example in;

Morton, N. 1987. Jurassic subsidence history in the Hebrides, N.W. Scotland.

Marine and Petroleum Geology vol. 4, pp. 226 -242.

You can also download through Research Gate

Dear Imran, I work in a thick alluvial plain (the Po plain Italy). It's composed by gravel, sands and clay and the total thick above the marine sediment could be more than 500 metres. My personal experience with 2D resistivity is not good ! No possibility to detect in a correct way the boundary between different lithology and different kind of answer respect presence or not presence of water. So I suggest you to approch another survey methodology !!! Paolo

If you are taking a short core <4ft a split spoon sampler works well.  One problem with extrusion is that the already compressed sample becomes further compressed, depending on what kind of organics are in the sediment.  I have not found a good way to apply a liner into the tubes because the forces of coring tend to rip the liners.

PVC is an easily melted solid. It seems that it would be possible to make a cutting jig that uses heated blades to melt/cut the core into halves (in a well ventilated area).  I usually work with aluminum pipe because they work well with vibracorers, PVC is to loosey goosey to get deep.

Depending on what kind of sledge corer you have it is possible to pre-split the PVC and apply hoops to keep it together during sampling.  When done simply remove the hoops.

Mean grain size (Mz) is the average grain-size. Several formulas are used in calculating the mean. The most inclusive graphically derived value is that given by Folk and Ward (1957): (Mz= (Φ16+ Φ50+Φ84)/3), where 16, 50, and 84 represent the size at 16, 50, and 84 percent of the sample by weight. Mean is also measured in phi units and is the most widely compared parameter. For more details you can see the following article: http://www.geo.mtu.edu/~raman/Ashfall/Syllabus/Entries/2009/6/21_GSD_files/GRADISTAT.pdf.

The phi scale (Krumbein, 1934) is a logarithmic transformation of the Wentworth (1922) grade scale based on the negative logarithm to the base 2 of the particle size. Φ = -log₂d(mm), and at the same time, you can easily find the diameter of particle in mm: d(mm) = 2^-Φ.

Best regards.

Amor DEGAICHIA

Sehr geehrter Herr Günther,

Dr. Towe has clearly mentioned the boundary at 110°C where per definition the water absorbed to the rock sample, whatever type it may be, is drawn. The other type of reaction to show a decomposition of the rock involving dehydration, decarbonization etc.  is placed under the header LOI (= loss on ignition).

Thermoanalytical methods like diffential thermal analysis (DTA) or thermogravimetry (TG)  reflect intracrystalline changes, involving among others the release of (OH)-, (CO3)--... which are typical of the minerals under study. See e.g. the classical book " Differential Thermal Analysis Application and Results in Mineralogy" published by Smykatz-Kloss, W. (1974)

You can use your own or "personal TG" by measurig the water released at various levels on temperature increase below 110°C.

Viel Glück !

Harald G. Dill

Hi Flora, at least the analytical protocoll has been described by the classical Cline (1969) paper and more recently summarized by Reese et al. (2011; Aquatic Geochemistry). Is this what you asked for? Best Michael

Milliman's work is still applicable to diverse platform settings!!

First of all, the 0.4g/cm2/y is a very high accumulation rate. It has all the three components (Lithogenic, biogenic and hydrogenic). you have to estimate the lithogenic fraction (river sediment) before calculating PAH input through river sediment. suppose you have lithogenic fraction accumulation of 0.2g/cm2/y and PAH concentration in lithogenic fraction (river sediment) is 656ng/g, then you multiply this two you will get PAH accumulation rate (131ng/cm2/y). But you can't extrapolate this value to whole basin by just multiplying with basin area. Because the river influence is high at its mouth then it decreases parallel and perpendicular to coast. so you should have sufficient data points all over sub marine fan to get a appropriate estimate.

From: https://www.researchgate.net/publication/240430744_Refinement_of_organic_methods_for_kerogen_characterization

"The amorphous kerogen components (amorphinite) are subdivided based upon fluorescence properties into fluoramorphinite (fluorescent) and hebamorphinite (non-fluorescent)."

Probably, the non-fluorescent Hebamorphinite is poor in fluorescent components ("live" hydrocarbons).

Therefore, it may represent "spent" source rock (a former source rock that expelled all possible hydrocarbons after reaching very high thermal maturity ).

Alternatively, a totally immature source rock would also contain no hydrocarbons.

It should be easy to establish, from the geological setting of your samples, if you are dealing with totally immature sediments from a thermal viewpoint, or nearly metamorphosed sediments.

 THANK YOU DEAR FREIND SO YOU MEAN HYDROCHEMICAL SIMULATION BY SATURATION INDEX CALCULATION M

Dear Mrs. Huang,

my colleagues and me elaborated a method which we used for diatomaceous earth and lacustrine sediment to quantify the amount of geogenic silica (= detrital quartz) and biogenic silica in test of floral and faunal microfossils. It can successfully be applied to genetic sedimentology and applied sedimentology:

DILL, H.G., STUMMEYER, J. and SIEWERS, U. (2002) Selective leaching of biogenic and geogenic silica in diatomaceous siliciclastics of the Kathmandu paleolake, Nepal.- Neues Jahrbuch für Mineralogie Mh., 2002 (1): 515-528.

You can download it from the RG server.

I wish you much success

H.G.Dill

…sedimentary shores dominated by infaunal bivalves and polychaetes. Macoma balthica probably is everywhere, Mya, Cerastoderma, etc. through most of area. A bit strange for me:   so many papers about North Atlantic intertidal communities lacking general definition of these communities. Especially for soft bottoms

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

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 Dr. Wang,

there is no "Philosopher´s Stone" or a single/ simple pathway to get precise information on the protoliths of metasedimentary rocks. The higher the grade of metamorphism and the more intensive the structural disturbances are the lower the probability of coming to grips with the original environment of deposition.

I suggest a series of approaches to be taken step by step which I listed from the small-scale to the large scale:

1. Consider the metamorphic rocks in question not as a separate entity but as part of a thick sedimentary pile. Make yourself acquainted with modern sedimentological facies analysis and geodynamic settings so as to see whether your models fit into modern-day environments of deposition or not (The present is the key to the past)

2. Given an isochemical process, collect as much as possible information from modern-day chemical facies analyses and compare it with point 1of your study area.

3. Try and find relic minerals in the metamorphic rocks which may be summarized under the header allochthonous and autochthonous heavy minerals. The first suite of minerals is source rock-related, the second one host-rock related, in other words in reflects processes within the depocenter. Do not only look at the mineral as a whole but also to the morphology and trace element contents of these minerals.

I think a general itinerary to the problem is much better at this moment than providing you with some triplots or cross plots. You must find your own way using this tripartite approach for your study site.

I wish you much success

H.G.Dill

Thin bedded coals are common in deep water sediments in th Kutai Basin, in the Makassar Straits, and offshore Sabah, in sediments mainly of Late Miocene age and form a major hydrocarbon source rock. These have been described by Rui Lin in Indonesian Petroleum Assn (IPA) proceedings and summarised by Saller et al in AAPG Bull.Also described from Sabah. Most organic matter is from angiosperm leaves. These have been illustrated in a paper by myself in IPA in 2011 which discusses the Neogene climate of Makassar Straits.

For such organic rich beds to occur in such abundance in deep marine sediments, you need a major sediment source from an area exhibiting a perhumid lowland equatorial climate, and most importantly this perhumid lowland climate needs to be maintained during periods of sea level lowstand, during which time extensive peat swamps formed around much of the coast of the island of Borneo (most lowstand tropical climates tended to be distinctly seasonal, and hence not peat forming - the Sunda region is the only low latitude area where lowstand peats are known to have widely formed during the Neogene). Coastal instability resulted in downslope transport of leaf-rich sediments in turbidite currents, with the leaf beds settling out typically just after the sands, and sometimes forming beds with a high organic carbon content, and mainly with liptinitic kerogens. Hyperpycnal processes may also be involved  

A confusing aspect of such successions is that due to the high input of organic matter, typical deep marine calcareous microfossils, such as benthonic forams, are missing due to dissolution. Nannofossils and planktonics may also be missing, with only agglutinated forams present. Dating is therefore difficult 

I am very interested to hear of any occurrences of leaf-rich deep marine thin bedded coals from any other areas

Dear Mr. Moradi,

the critical parameters to give a general answer to your question is the ratio between weathering intensity (physical+chemical) and vertical displacement (uplift in the provenance area + subsidence in the depocenter). If we ignore the physical part of weathering, the parameter which counts is the ratio between uplift/erosion and chemical weathering which depends upon the climatic conditions and in general increases from the pole to the ecquator.

Erosion and weathering are to different processes which work separately from each other.

Your problem has to be discussed from a more geodynamic point of view.

It is the interplay of geology and geomorphology that is reflected in the rate of uplift and weathering. Geodynamic setting, regional geology and geomorphology are closely linked with each other and necessarily have to play hand in hand to concentrate and preserve a zone of chemical weathering . Modern fold belts still on the rise like the Alpine -Central Asian fold belt or the Andes extending along an active plate margin are less likely to provide good conditions for large regolith deposits in the hinterland, even if these geodynamic settings are located in a morphoclimatic zone most suitable for chemical weathering. In contrast, cratonic crustal sections stable over a long period of time with little vertical displacement and passive margin geodynamic settings are preferred crustal sections for thick regolith deposition and preservation. The interaction of vertical displacement and of chemical weathering are decisive for the accumulation and preservation. During slow uplift, chemical weathering operative in the peneplai¬ned hinterland and on the sedimentary bodies in the foreland are instrumental during decomposition of labile constituents from the parent material and their well-balanced interaction enhance the quality and increase the thickness of the residual clay deposits. With increasing rate of uplift, the trend is reversed. Reducing the slope angle or the paleogradient, or in other words moving from the alluvial-colluvial fan system , through the alluvial-fluvial systems into deltaic and swampy rises the likelihood of delineating clay concentration of economic significance like black shales.

As long as your geodynamic setting is not disclosed to the audience I can give you only this general answer.

Best regards

H.G.Dill

Hi Anne-Marie

The films are poorly crystalline Fe oxyhydroxide minerals formed by iron oxidising bacteria such as Leptothrix and Gallionella.  I can send you a paper on their mineralogy if you are interested

Regards

Steve Appleyard

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).