Effect Of Mineral Matrix Research Articles

Structural and chemical variability and provenance of lacustrine organic matter in the Miocene Nördlinger Ries post-impact sediments

The Nördlinger Ries in southern Germany contains a sequence of Miocene post-impact lacustrine sediments. To gain knowledge on the chemical composition and provenance of the organic matter (OM) through the up to 250 m thick sediment profiles, pyrolytic, organic geochemical and infrared spectroscopy measurements were performed on both sediments and concentrated OM. Type I kerogen prevails through the examined samples with high atomic H/C ratios (1.6 on average), hydrogen index (HI mostly >600 mg HC/g TOC), and spectral A- and C-factor values (mostly >0.8), but low oxygen index values (OI mostly <25 mg CO2/g TOC) for the concentrated OM. Exceptions occur in the uppermost Miocene sediments at the central site (Nördlingen-1973) and some marginal (SUBO-18) sediments containing hydrogen-lean type III kerogen having low H/C ratios (<1), HI (<300 mg HC/g TOC), spectral A- and C-factor values (<0.6), but high OI values (>40 mg CO2/g TOC). Mineral matrix effects induced by abundant clay minerals and zeolites significantly reduce the HI of bulk sediments as compared to concentrated OM. Organic sulfur-rich kerogen occurs in the basal units in the NR-1973 and occasionally in the SUBO-18 boreholes with high atomic Sorg/Corg ratios >0.04 and pyrolytic thiophenes/toluene ratio > 13. Abundant pyrolytic alkanes/alkenes, high spectral A-factor and CH2/CH3 values suggest prominent algal input to the OM for most of the samples. The aliphatic chain length of the kerogen decreases and the branching degree increases from the older, deeper to the younger, shallower deposits. While oxygen-bearing organic constituents are common, nitrogen-bearing moieties are rare. A general structural model is established for the type I sulfur-rich, Miocene kerogen of the Nördlinger Ries paleo-lake.

Mineral Matrix Effects on Pyrolysis Products of Kerogens Infer Difficulties in Determining Biological Provenance of Macromolecular Organic Matter at Mars.

Ancient martian organic matter is likely to take the form of kerogen-like recalcitrant macromolecular organic matter (MOM), existing in close association with reactive mineral surfaces, especially iron oxides. Detecting and identifying a biological origin for martian MOM will therefore be of utmost importance for life-detection efforts at Mars. We show that Type I and Type IV kerogens provide effective analogues for putative martian MOM of biological and abiological (meteoric) provenances, respectively. We analyze the pyrolytic breakdown products when these kerogens are mixed with mineral matrices highly relevant for the search for life on Mars. We demonstrate that, using traditional thermal techniques as generally used by the Sample Analysis at Mars and Mars Organic Molecule Analyser instruments, even the breakdown products of highly recalcitrant MOM are transformed during analysis in the presence of reactive mineral surfaces, particularly iron. Analytical transformation reduces the diagnostic ability of this technique, as detected transformation products of both biological and abiological MOM may be identical (low molecular weight gas phases and benzene) and indistinguishable. The severity of transformational effects increased through calcite < kaolinite < hematite < nontronite < magnetite < goethite. Due to their representation of various habitable aqueous environments and the preservation potential of organic matter by iron, it is not advisable to completely avoid iron-rich strata. We conclude that hematite-rich localities, with evidence of extensive aqueous alteration of originally reducing phases, such as the Vera Rubin Ridge, may be relatively promising targets for identifying martian biologically sourced MOM.

Hydrocarbon source rocks in Kazhdumi and Pabdeh formations—a quick outlook in Gachsaran oilfield, SW Iran

Geochemical study of Kazhdumi and Pabdeh Formations as potential source rocks in Gachsaran Oilfield demonstrates that the Kazhdumi Formation has a fair to good capability of hydrocarbon generation and predominately contains type II-III kerogen. On the other hand, the Pabdeh Formation has a poor to good petroleum potential and contains different kerogen types, including type II, type II-III, type III and even for one sample, type IV, indicating different depositional conditions for this formation. The geochemical log of the Kazhdumi Formation shows that there is a close correlation between different geological parameters as noticed prominently in well number 55, which suggests the more extensive the anoxic condition, the higher the petroleum potential is for Kazhdumi Formation. By contrast, a poor correlation between TOC and other Rock–Eval-derived parameters for the Pabdeh Formation at a depth of more than 2100 m may demonstrate the inert organic matter and mineral matrix effects at this depth interval. However, biomarkers show differences in lithology and depositional environment for the Kazhdumi Formation in well numbers 55 and 83. On the other hand, the Pabdeh Formation has a mixed lithology (carbonate-shale) deposited in a marine setting under suboxic–anoxic condition. Moreover, thermal maturity indicators suggest that Pabdeh and Kazhdumi Formations are immature and early mature, respectively.

A new resource assessment workflow to achieve gas risk and phase-specific source potential indices

Accurate estimation of source rock potential has been a challenge, especially when a mineral matrix effect (MME) may influence the source rock potential estimation process. A recent study has proposed a new workflow based on custom organofacies classification to obtain a more accurate evaluation of lacustrine source rock potential. However, their workflow was not demonstrated on more commonly occurring marine source rocks. This study aims to better characterize marine source rocks, and additionally presents phase-specific Source Potential Index (SPI), SPIoil and SPIgas, and a new parameter called the Gas Risk Index (GRI). The methodology outlined in this study begins with an organofacies characterization based on both Rock-Eval pyrolysis and palynofacies analyses on samples from an offshore northwestern African well. Then, empirical laws are proposed to correct the MME to attain an improved source rock potential and calculate the new indices SPIoil, SPIgas, and GRI. The results demonstrate that most of the samples with HI values between 400 and 500 mg/gC, usually associated with a terrestrial-marine mixture (gas- and oil-prone), are actually composed of an altered marine organic matter (oil-prone) in the basin studied. It was observed that the MME lowered the S2 and HI values of samples with TOC up to 7 wt% in the study well, thereby underestimating the overall generative potential of the samples. This led to misidentification of organofacies based on lowered HI values, resulting in an inaccurate determination of liquid and gas prone nature of the source rock, which directly impacts the SPI values, increasing the risk of incorrect assessment. Therefore, the use of both palynofacies and pyrolysis data is recommended in differentiating terrestrial-marine mixtures from altered marine organic matter, and in correcting the MME to obtain reliable SPI values. This study presents a case for a new sample analysis workflow, which includes correction for the MME, refined organofacies classification, and determination of gas risk.

Comparative geochemical and pyrolytic study of coals, associated kerogens, and isolated vitrinites at the limit between subbituminous and bituminous coal

A sample set consisting of coal, overlying and intercalating siliciclastic rocks and kerogen concentrated from these rocks of nine Pennsylvanian subbituminous to bituminous coal seam intervals from the German Ruhr Basin was analysed in order to detect chemical structural differences of the organic matter. Vitrinites from the coal seams and the kerogen concentrates were isolated to study effects of maceral group composition on chemical properties of typical type III kerogen. Rock-Eval Tmax values of sediment samples are higher than both those of the kerogen concentrated from them and associated coal samples. This is a result of the mineral matrix effect. Higher OI values of the sediment and kerogen samples as compared to those of the bulk coal samples cannot be explained by the abundance of carbonyl/carboxyl groups as reflected by results obtained by attenuated total reflectance (ATR) FT-IR spectroscopy. Ratios of the areas of the aromatic γCH out of plane, the aliphatic νCHx stretching, and the aromatic νC=C ring stretch regions imply a lower degree of aromaticity and at the same time higher degree of condensation of vitrinites originated from the sedimentary layers, respectively. Upon Curie Point (CP) pyrolysis at 590 °C, these vitrinite samples generate higher amounts of long-chained normal alkanes and n-alkenes than the bulk samples or the vitrinite originating from the coals. While reflectance values of vitrinites from coals and sedimentary layers are within the standard deviation of values expected for the narrow maturity window, only the vitrinites of the coal seams show some correlation with depth. Clearly, the relative abundance of phenols is decreasing with increasing maturity, as well as the ratio of benzenes over higher condensed aromatic moieties as revealed by their pyrolysis products generated at 764 °C.

Comparative study between sequential solvent-extraction and multiple isothermal stages pyrolysis: A case study on Eocene Shahejie Formation shales, Dongying Depression, East China

Chemical and thermal extractions were performed on a suite of 23 shale core samples, from the Eocene Shahejie Formation of the Dongying Depression, East China, to investigate the Oil-In-Place of shales and the difference among various assessment approaches. The novel multiple isothermal stages (MIS) pyrolysis [Romero-Sarmiento et al., AAPG European Regional Conference & Exhibition. Lisbon; 2015] derives four peaks characterizing the light, light to medium, heavier- and non- hydrocarbons, and the pyrolyzed hydrocarbon (i.e., hydrocarbons derived from thermal decomposition of kerogen), respectively. Compared with standard Rock-Eval pyrolysis on OIP estimation, the MIS pyrolysis provides more specific information concerning gross compositions and physical status of oils, which reduces the impact of the frequently-occurred carryover effect to a certain extent. Systematic variations of molecular compositions especially the light vs. heavy n-alkanes have been elucidated. The mobile oil estimated from MIS pyrolysates is very close to solvent extractable oils (i.e., bitumen). Abnormal increase of pyrolysis hydrocarbons after initial extraction is attributed to the mineral matrix effect. This study demonstrated discrepancies between various approaches in assessment of thermo-vaporizable and pyrolysis hydrocarbons within shale reservoirs and triggered a re-understanding on the application of pyrolysis parameters in shale oil systems.

Influence of inherent mineral matrix on the product yield and characterization from Huadian oil shale pyrolysis

Huadian oil shale was subjected to step-wise acid treatment to remove inherent carbonate and silicate minerals. The original oil shale and its demineralization products (carbonate- and carbonate-silicate-free oil shale samples) were pyrolyzed in a fixed-bed pyrolyzer to determine the mineral matrix effect on product yield and characteristics of shale oil and gases. The shale oil yields of original, carbonate-free, and carbonate-silicate-free oil shale samples were 50.4 wt.%, 44.3 wt.%, and 50.3 wt.% (values on dry and mineral matter-free basis), respectively, which indicated that carbonates promote, while silicates suppress, shale oil production. Coking of aromatic compounds appeared to be the dominant mechanism accounting for the variation of the shale oil yield. Elimination of the carbonate minerals decreased the nitrogen- and oxygen-containing compounds of shale oil, while removal of silicates increased the oxygenated compounds. Both carbonate and silicate minerals decreased the atomic H/C ratio of shale oil. Silicates promoted the cracking and aromatization of aliphatic hydrocarbons, which increased the short-chain aliphatic hydrocarbons and aromatic hydrocarbons of shale oil, as well as C1–C4 hydrocarbons and H2 yields. On the contrary, carbonates suppressed the cracking of long chain aliphatic hydrocarbons.

Effects of a high level of phytase on broiler performance, bone ash, phosphorus utilization, and phytate dephosphorylation to inositol.

An experiment was conducted to evaluate how the addition of microbial phytase influenced growth performance, bone mineralization, tissue P content, apparent digestibility and retention, and inositol phosphate (IP) concentrations in broilers fed diets with varying mineral matrices from 2 to 23 d of age. At 2 d of age, chicks were randomly allotted to receive 1 of 6 experimental diets arranged as a 3 × 2 factorial of mineral matrix [control diet with 1.0% Ca and 0.5% non-phytate phosphorus (NPP); mineral matrix 1 with 0.84% Ca and 0.35% NPP; and mineral matrix 2 with 0.77% Ca and 0.29% NPP] and phytase supplementation (0 or 1,500 FTU/kg). Feed intake was influenced (quadratic, P = 0.012) by the mineral matrix, but no interaction or main effect of phytase were observed. Phytase increased (P = 0.011) BW gain regardless of the mineral matrix applied. Feed efficiency was not influenced (P >0.05) by mineral matrix, phytase, or their interaction. Phytase increased bone ash content differentially across matrices (interaction, P <0.01), and tibia P content was lowest in birds fed matrix 2 and highest in the control (linear, P <0.05). Concentrations of P in muscle, spleen, and liver were not affected by treatment. An interactive effect (P <0.01) was observed for apparent ileal digestibility (AID) of P, where phytase increased AID in matrix 1. An interactive effect (P <0.01) was observed for apparent retention of P and Ca, where phytase reduced P and Ca retention in the control diet. A main effect (P <0.01) of mineral matrix was observed for AID of Ca, with birds fed matrix 1 having the lowest AID of Ca compared with control and matrix 2 treatments. Phytase influenced (P <0.05) IP concentrations differently across matrices. Overall, phytase and the mineral matrix, either as main effects or in an interactive manner, influenced growth performance, apparent nutrient digestibility and retention, bone and IP concentration responses in broiler chicks.

The influence of shale depositional fabric on the kinetics of hydrocarbon generation through control of mineral surface contact area on clay catalysis

Accurately assessing the temperature and hence the depth and timing of hydrocarbon generation is a critical step in the characterization of a petroleum system. Clay catalysis is a potentially significant modifier of hydrocarbon generation temperature, but experimental studies of clay catalysis show inconsistent or contradictory results. This study tests the hypothesis that source rock fabric itself is an influence on clay mineral catalysis as it controls the extent to which organic matter and clay minerals are physically associated. Two endmember clay-organic fabrics distinguish the source rocks studied: (1) a particulate fabric where organic matter is present as discrete, >5 μm particles and (2) a nanocomposite fabric in which amorphous organic matter is associated with clay mineral surfaces at sub-micron scale. High-resolution electron imaging and bulk geochemical characterisation confirm that samples of the Miocene Monterey Formation (California) are representative of the nanocomposite source rock endmember, whereas samples from the Permian Stuart Range Formation (South Australia) represent the particulate source rock endmember. Kinetic experiments are performed on paired whole rock and kerogen isolate samples from these two formations using open system, non-isothermal pyrolysis at three different heating rates (0.7, 2 and 5 K/min) to determine the effects of the different shale fabrics on hydrocarbon generation kinetics. Extrapolation to a modelled geological heating rate shows a 20 °C reduction in the onset temperature of hydrocarbon generation in Monterey Formation whole rock samples relative to paired kerogen isolates. This result is consistent with the Monterey Formations’s nanocomposite fabric where clay catalysis can proceed because reactive clay minerals are intimately associated with organic matter. By contrast, there is no significant difference in the modelled hydrocarbon generation temperature of paired whole rock and kerogen isolates from the Stuart Range Formation. This is consistent with its particulate fabric, where relatively large, discrete organic particles have limited contact with the mineral matrix and the clay minerals are mainly diagenetic and physically segregated within pores. While heating rate may have a control on mineral matrix effects, this result shows that the extent to which organic matter and clay minerals are physically associated could have a significant effect on the timing of hydrocarbon generation, and is a function of the depositional environment and detrital vs diagenetic origin of clay minerals in source rocks.

Organic Matter Detection on Mars by Pyrolysis-FTIR: An Analysis of Sensitivity and Mineral Matrix Effects.

Returning samples from Mars will require an effective method to assess and select the highest-priority geological materials. The ideal instrument for sample triage would be simple in operation, limited in its demand for resources, and rich in produced diagnostic information. Pyrolysis–Fourier infrared spectroscopy (pyrolysis-FTIR) is a potentially attractive triage instrument that considers both the past habitability of the sample depositional environment and the presence of organic matter that may reflect actual habitation. An important consideration for triage protocols is the sensitivity of the instrumental method. Experimental data indicate pyrolysis-FTIR sensitivities for organic matter at the tens of parts per million level. The mineral matrix in which the organic matter is hosted also has an influence on organic detection. To provide an insight into matrix effects, we mixed well-characterized organic matter with a variety of dry minerals, to represent the various inorganic matrices of Mars samples, prior to analysis. During pyrolysis-FTIR, serpentinites analogous to those on Mars indicative of the Phyllocian Era led to no negative effects on organic matter detection; sulfates analogous to those of the Theiikian Era led, in some instances, to the combustion of organic matter; and palagonites, which may represent samples from the Siderikian Era, led, in some instances, to the chlorination of organic matter. Any negative consequences brought about by these mineral effects can be mitigated by the correct choice of thermal extraction temperature. Our results offer an improved understanding of how pyrolysis-FTIR can perform during sample triage on Mars. Key Words: Mars—Life-detection instruments—Search for Mars’ organics—Biosignatures. Astrobiology 16, 831–845.

Some Predicted Effects of Minerals on the Generation of Petroleum in Nature

The presence of some minerals can strongly influence the composition of laboratory pyrolysates. The question is whether similar effects may also occur in nature, thereby influencing the gas–oil ratio and other bulk compositional characteristics. A series of experiments have been conducted at varying heating rates to examine this issue. Three source rocks that vary significantly in mineralogy (a quartz-rich, a calcite-rich, and a clay-rich sample), namely, the Alum shale, Bowland shale, and Toolebuc oil shale, respectively, were tested by Rock-Eval pyrolysis, open-system pyrolysis gas chromatography (PyGC). and bulk kinetic parameters to check for the existence or otherwise of mineral matrix effects (MMEs). Kerogen and whole-rock samples were then pyrolyzed at three heating rates using closed-system [microscale sealed vessel (MSSV)] pyrolysis to examine the heating rate dependency upon hydrocarbon aromaticity, gas–oil ratio, and total yield. The solvent extract of one Bowland shale sample was used as a ref...

Pilot for Validation of Online Pretreatments for Analyses of Organics by Gas Chromatography-Mass Spectrometry: Application to Space Research.

The search for complex organic molecules in extraterrestrial environments, including important biomolecules such as amino and fatty acids, will require a space compatible sample handling system to enable their detection by gas chromatography-mass spectrometry (GC-MS). For the future Mars exploratory mission Exomars 2018 aimed at organic molecules detection, a dedicated laboratory pilot, called Device for Pretreatment of Sample (DPS), reproducing representative space operating conditions has been developed. After its optimization, it aimed at validating under development protocols and interpreting forthcoming in situ resulting data. The DPS, dedicated to organic compounds' analysis, is discussed in terms of its technical features. The derivatization is carried out on a 50-100 mg mineral sample in a 4 mL reactor coupled with a GC-MS injector to simulate on line in situ derivatization-volatilization-transfer steps. Three derivatization reactions have been carried out with N-methyl-N-(tert-butyldimethylsilyl)-trifluoroacetamide (MTBSTFA) as silylating reagent, N,N-dimethylformamide dimethylacetal (DMF-DMA) and tetramethylammonium hydroxide (TMAH) as methylating agents. The performances are illustrated by comparison of conventional and in situ silylation, developed for space research applications, using terrestrial mineral matrix and Mars analog materials enriched with 25 nmol of each targeted organic molecule. The work presented in this rationale has established that the use of derivatization reactions widens the scope of targeted molecules but also clearly points out mineral matrix effect. Decreasing mineral influence on pretreatment will be the next scientific challenge in in situ analysis.

Evaluation of source rock potential, matrix effect and applicability of gas oil ratio potential factor in Paleocene–Eocene bituminous shales of Çamalan Formation, Nallıhan – Turkey

In order to improve the reliability and accuracy of source rock evaluation, a total of 102 shale samples of Çamalan Formation were collected, analyzed and re-characterized with taking matrix retention effect into account. Results from Rock-Eval and visual kerogen analyses indicate: 1. an excellent source rock with an average TOC of 6.39 wt.%. 2. An assemblage of amorphous (i.e., alginite, type I) organic matter as a major organic constituent with an excellent potential for generating oil. 3. Shale samples from Çamalan Formation are in immature/early–intermediate stage of maturity based on Tmax (Avg. ∼440 °C) and spore color index (SCI ∼2.5–4). Also no amount of Çamalan generated oils are migrated out of shale based on S1 vs. TOC plot. (i.e., Transformation ratio (TR ∼0)). Samples of this study show a significant mineral matrix effect. After correction of mineral matrix effect the average hydrogen index (HI) of the Çamalan Formation increased by more than 60 mg HC/g TOC and reached to an average of 811 mg HC/g TOC. Gas oil ratio potential (GORP) factor were used in order to split up the TOC and S2 into oil-prone and gas-prone and also to investigate the level of consistency between the results of GORP factor and those of visual kerogen studies. Based on obtained GORP factor more than 90% of TOC(live) is composed from oil-prone materials which is in acceptable agreement with petrographic assessments.

EVALUATION OF THE HYDROCARBON POTENTIAL, MINERAL MATRIX EFFECT AND GAS-OIL RATIO POTENTIAL OF OIL SHALE FROM THE KABALAR FORMATION, GÖYNÜK, TURKEY

The present study focuses on the evaluation of the hydrocarbon potential, retention effect of mineral matrix and the gas-oil ratio potential (GORP) of oil shale from the Kabalar Formation in the Goynuk area, Turkey, to assess the quality of its organic matter. The results of Rock-Eval pyrolysis generally suggest relatively high organic carbon content (TOC) for Kabalar oil shale, ranging from 1 to 13.23 wt%. These values are consistent with data on source rocks that may have a good to excellent source rock potential. The kerogen in Kabalar oil shale was characterized based on Hydrogen Index (HI) value, S2/S3 ratio, and organic petrographic studies. The results indicate that most of the studied samples are characterized as containing oil prone (type I and II kerogen) organic matter. The low spore color index (SCI) and high S2/S3 ratio with a commonly low Tmax (< 440 °C) demonstrate that most of the oil shale samples are in the immature to early mature stages of thermal maturity. After calculating the transformation ratio (TR), the oil shale samples were divided into mature (TR = 0.2) and immature (TR = 0) subdivisions in order to take the maturity effects on organic carbon content (TOC) and hydrocarbons retention into account and also select the appropriate GORP overlay. After correcting the mineral matrix effect in the immature subdivision, the mean HI value of the Kabalar Formation increased by about 268 and reached 855 mg HC/g TOC. Due to the relatively higher thermal maturity values, the mineral matrix effect is minimized in the mature subdivision. Based on GORP factor, the TOC(live) of Kabalar oil shale is composed only of oil prone material, which is in good agreement with the results inferred from organic petrographic and pyrolysis studies.

XRD and TG-FTIR study of the effect of mineral matrix on the pyrolysis and combustion of organic matter in shale char

Shale char organic matter was obtained by demineralization of shale char through HCl and HF treatment. XRD technique was applied to determine the minerals in shale char and its ashes from different-temperature combustions. The effect of mineral matrix in shale char on the pyrolysis and combustion of organic matter was explored by the TG-FTIR test to shale char and its organic matter. Minerals in shale char ash changed both in amount and variety during combustion. Both the pyrolysis and combustion of shale char and its organic matter can be divided into two stages. Without confinement of mineral matrix after demineralization, the emission of gaseous products from the pyrolysis of shale char organic matter starts earlier than that of shale char pyrolysis. The effect of inorganic minerals on the oxidation of organic matter displays in two aspects. For one, the earth metal cations contained in inorganic minerals may promote the oxidation of organic matter. Secondly, the presence of inorganic matrix enhances the porosity of shale char. New organic sulfur formed during oil shale retorting is confined by inorganic matrix during combustion. After demineralization, this new organic sulfur can decompose and be released intensively at low temperature.

Maturity and Source Rock Evaluation of the Gadvan Formation, Persian Gulf, South of Iran

Rock-eval pyrolysis is used to rapidly evaluate the petroleum generation potential and maturity of rocks. In the current paper, the geochemical characteristics of a probable source rock, Gadvan Formation, in south of Iran, Persian Gulf, was studied. To get the goal 56 ditch-cutting samples of 17 wells, drilled in Persian Gulf, were collected and analyzed using Rock-Eval pyrolysis. Pre-analyses of Rock-Eval outputs shows that only 33 samples are suitable for further investigations, as other ones has been contaminated by migrated hydrocarbons. Kerogen type III is dominating type in the samples, while few of them are type II. It seems that Gadvan is a gas prone formation, which can generate hydrocarbon due to its fair maturity in some intervals. The possible organic facies of Gadvan Formation are mainly reducing and deep marine environments with moderate rate of sedimentation, which confirm its potential to perform as a source rock in the area; however, few of samples were deposited in oxidizing condition based on the results of Jones diagram. Finally, the diagram of S2 versus total organic carbon proved negligible mineral matrix effect and inert carbon in the understudied samples of Gadvan.

Using Rock Eval Pyrolysis for Studying the Hydrocarbon Potential of the Pabdeh Formation in Ziluee Oilfield, South West of Iran

The author discusses the hydrocarbon potential of Pabdeh formation in Ziluee oilfield, in southwest Iran. The research was focused on characterization of this formation based on Rock-Eval (RE) pyrolysis, which is an effective instrument for analyzing probable source rock. Various diagrams were employed for interpreting the raw outputs of RE. The results revealed that kerogen type II and III are mainly distributed in understudied cuttings; therefore, Pabdeh can produce oil and gas in Ziluee oilfield, while its genetic potential is fair to good and maturation level is high enough. Based on RE data and lithological studies, Pabdeh was divided into three important zones, A, B, and C. Zone B is the most effective zone for producing oil, whereas zones A and C mainly produced gas in the proposed oilfield. Jones diagram showed that different intervals of this formation were not deposited in a singular environment. Some intervals belonged to a reducing lacustrine marine and some of them deposited in terrigenous oxidizing condition. Finally, the effect of mineral matrix and amounts of inert carbon in the samples was calculated. The small value of mineral matrix effect indicates that small amount of hydrocarbon was absorbed by minerals during pyrolysis. In addition, amount of inert carbon is negligible in studied samples of Pabdeh formation.

Linking temperature sensitivity of soil organic matter decomposition to its molecular structure, accessibility, and microbial physiology

Temperature sensitivity of soil organic matter (SOM) decomposition may have a significant impact on global warming. Enzyme-kinetic hypothesis suggests that decomposition of low-quality substrate (recalcitrant molecular structure) requires higher activation energy and thus has greater temperature sensitivity than that of high-quality, labile substrate. Supporting evidence, however, relies largely on indirect indices of substrate quality. Furthermore, the enzyme-substrate reactions that drive decomposition may be regulated by microbial physiology and/or constrained by protective effects of soil mineral matrix. We thus tested the kinetic hypothesis by directly assessing the carbon molecular structure of low-density fraction (LF) which represents readily accessible, mineral-free SOM pool. Using five mineral soil samples of contrasting SOM concentrations, we conducted 30-days incubations (15, 25, and 35°C) to measure microbial respiration and quantified easily soluble C as well as microbial biomass C pools before and after the incubations. Carbon structure of LFs (<1.6 and 1.6-1.8gcm(-3) ) and bulk soil was measured by solid-state (13) C-NMR. Decomposition Q10 was significantly correlated with the abundance of aromatic plus alkyl-C relative to O-alkyl-C groups in LFs but not in bulk soil fraction or with the indirect C quality indices based on microbial respiration or biomass. The warming did not significantly change the concentration of biomass C or the three types of soluble C despite two- to three-fold increase in respiration. Thus, enhanced microbial maintenance respiration (reduced C-use efficiency) especially in the soils rich in recalcitrant LF might lead to the apparent equilibrium between SOM solubilization and microbial C uptake. Our results showed physical fractionation coupled with direct assessment of molecular structure as an effective approach and supported the enzyme-kinetic interpretation of widely observed C quality-temperature relationship for short-term decomposition. Factors controlling long-term decomposition Q10 are more complex due to protective effect of mineral matrix and thus remain as a central question.

A TG–FTIR investigation to the catalytic effect of mineral matrix in oil shale on the pyrolysis and combustion of kerogen

A demineralized Huadian oil shale sample, p-kerogen, is obtained through HCl&HF treatment. The XRD test for oil shale identifies the minerals in it. The catalytic effect of minerals in oil shale on the pyrolysis and combustion of kerogen is investigated through the TG–FTIR test to original oil shale and p-kerogen. The resultant effect of all minerals in oil shale promotes the decomposition and release of the organic matter in the sample during the pyrolysis. The promoting effect of minerals on the oxidation of kerogen expresses in two aspects: on the one hand, the catalytic effect of minerals makes more organic matter oxidized in the first oxidation stage; on the other hand, the presence of inorganic framework creates the additional porosity in oil shale after the first oxidation stage, which significantly decreases the resistance of oxygen diffusing into the inner of sample particles. Part of the pyrite in the sample will be converted into new organic sulfur compounds in the absence of other minerals while most of pyritic sulfurs are oxidized into SO2 directly and then deposited within sample particles in the presence of minerals during the combustion.

Planning for Mars Returned Sample Science: Final Report of the MSR End-to-End International Science Analysis Group (E2E-iSAG)

Returning samples from Mars to Earth for scientific analysis has been, and continues to be, among the highest priority objectives of planetary science. Partly for this reason, the 2011 Planetary Science Decadal Survey placed high priority on a proposed 2018 rover mission that would conduct careful in situ science and use that scientific information to select and cache samples that could be returned to Earth by a potential future mission. In order to ensure that the potential contributions of the 2018 rover to the proposed MSR Campaign are properly planned, this study was undertaken to consider the science of the MSR Campaign concept from end to end. This white paper is the principal output of the Mars Sample Return (MSR) End-to-End International Science Analysis Group (E2E-iSAG): a group chartered by MEPAG (Mars Exploration Program Analysis Group).