Thermal maturity,source rock potential and kinetics of hydrocarbon generation in Permian shales from the Damodar Valley basin,Eastern India     

《Marine and Petroleum Geology》2015

This study investigates the source rock characteristics of Permian shales from the Jharia sub-basin of Damodar Valley in Eastern India. Borehole shales from the Raniganj, Barren Measure and Barakar Formations were subjected to bulk and quantitative pyrolysis, carbon isotope measurements, mineral identification and organic petrography. The results obtained were used to predict the abundance, source and maturity of kerogen, along with kinetic parameters for its thermal breakdown into simpler hydrocarbons.The shales are characterized by a high TOC (>3.4%), mature to post-mature, heterogeneous Type II–III kerogen. Raniganj and Barren Measure shales are in mature, late oil generation stage (Rr%_Raniganj = 0.99–1.22; Rr%_{Barren Measure} = 1.1–1.41). Vitrinite is the dominant maceral in these shales. Barakar shows a post-mature kerogen in gas generation stage (Rr%_Barakar = 1.11–2.0) and consist mainly of inertinite and vitrinite. The δ¹³C_org value of kerogen concentrate from Barren Measure shale indicates a lacustrine/marine origin (−24.6–−30.84‰ vs. VPDB) and that of Raniganj and Barakar (−22.72–−25.03‰ vs. VPDB) show the organic provenance to be continental. The δ¹³C ratio of thermo-labile hydrocarbons (C₁–C₃) in Barren Measure suggests a thermogenic source.Discrete bulk kinetic parameters indicate that Raniganj has lower activation energies (ΔE = 42–62 kcal/mol) compared to Barren Measure and Barakar (ΔE = 44–68 kcal/mol). Temperature for onset (10%), middle (50%) and end (90%) of kerogen transformation is least for Raniganj, followed by Barren Measure and Barakar. Mineral content is dominated by quartz (42–63%), siderite (9–15%) and clay (14–29%). Permian shales, in particular the Barren Measure, as inferred from the results of our study, demonstrate excellent properties of a potential shale gas system.  相似文献   

Geochemistry and origin of the Cretaceous sedimentary kaolin deposits,Red Sea,Egypt     

Hassan M. Baioumy 《Chemie der Erde / Geochemistry》2014

This work reports, for the first time, the mineralogical and geochemical characteristics of the Cretaceous sedimentary kaolin deposits in the Red Sea area, Egypt and sheds the light on their source. Mineralogical and geochemical analyses of both bulk deposits and the sand and clay fractions of these deposits indicated that they are composed of kaolinite (average of 75 wt.%) and quartz (average of 22 wt.%). Traces of anatase (average of 1 wt.%) were identified in all kaolin samples, while traces of halite (average of 2 wt.%) and hematite (average of 1 wt.%) were reported in the majority of the analyzed samples. The clay fractions show relatively high contents of TiO₂ (average of 2.1%), Ni (average of 103 ppm), Nb (average of 98 ppm), Y (average of 67 ppm), and Zr (average of 630 ppm). Sum of the rare earth elements (ΣREE) in the clay fractions varies between 193 and 352 ppm. Chondrite-normalized REE patterns show enrichment of the light REE relative to the heavy REE ((La/Yb)_N = 9) and negative Eu anomaly (Eu*/Eu = 0.67).  相似文献   

Perspectives for Li- and Ta-Mineralization in the Borborema Pegmatite Province,NE-Brazil: A review     

《Journal of South American Earth Sciences》2014

The increasing strategic importance of Li- and Ta-ores during the last decades due to the strong consumption growth for rechargeable batteries and high temperature and corrosion resistant capacitors reactivated the interest of studies in pegmatite fields around the world, because these rocks supply respectively 25% and 100% of the world consumption in these elements. Research on petrogenetic issues and major and accessory mineral chemistry variations in rare element (REL)-pegmatites of the Borborema Pegmatite Province in Northeast Brazil were tested as tools for the diagnosis of the metallogenetic potential of rare metals in individual pegmatites and in the province as a whole along the last dozen of years. The results allowed to establish the nearly isobaric (3.8 kbar) crystallization conditions of the REL-pegmatites between approximately 580 °C (liquidus) and 400 °C (solidus) from a peraluminous melt saturated in an aquo-carbonic medium to low salinity volatile phase and an immiscible peralkaline flux-enriched (H₂O, CO₂, F, B, Li etc.) melt fraction, based on melt and fluid inclusion studies. Mineral-chemistry data from 30 selected REL-pegmatites in the province allowed to classify three of them as being of the complex-spodumene or -lepidolite subtype in Černý's classification. Both subtypes are supposed to be potentially fertile, (highly fractionated, and with good chances to bear Li- and Ta-ore concentrations). It was also possible to identify several pegmatitic granite intrusions with textural and lithogeochemical characteristics also found in source granites of REL-pegmatite provinces elsewhere. Preliminary chemical Pb/U/Th geochronological determinations in uraninite and xenotyme crystals of these granites indicate an age of 520 ± 10 Ma and match recently published Ar/Ar in mica and U/Pb ages in columbite-group minerals (CGM) of the REL-pegmatites between 509 and 525 Ma. Mineral-chemistry data from grains of the outer zones of the pegmatites do not allow to distinguish potentially fertile from barren pegmatites. This discrimination is possible only if samples of the inner intermediate zone, replacement pockets or quartz core are used. From the tested minerals trace-element determinations (mainly Li, Al, Ti, Ge, B among 14 tested elements) by LA-ICP-MS technique in quartz seem to be more efficient than the classical approach (of Rb, K, Cs, Ga, Sr Ta) in K-feldspar or micas, due to the susceptibility to hydrothermal or supergene alteration of the latter. Mineral-chemistry variations in CGM, tourmalines, garnet and gahnite turned out to be efficient discriminators but all of them have the disadvantage of an eventual and, if present, random distribution, typical for accessory minerals in pegmatites, not allowing a regular sampling in most cases. Additional tests are recommended to confirm respectively the preliminary results of mineral-chemistry as exploration tools on a larger number of pegmatites and geochronological data to confirm the existence of another, older, synorogenetic generation of REL-pegmatites in the BPP.  相似文献   

BIF成因研究进展   总被引：5，自引：0，他引：5       下载免费PDF全文

刘利  张连昌  代堰锫 《地质科学》2014,(3):1018-1033

BIF在全球广泛分布,BIF型铁矿是铁的重要来源。根据产出的构造背景将其分为阿尔戈玛型（Algoma-type）和苏必利尔湖型（Lake Superior-type）。BIF主要产出于前寒武纪的古老克拉通和/或年轻地体,形成时代集中在3.0～2.0 Ga,峰期为2.5 Ga左右。前人对BIF型铁矿的成因研究着重于BIF的物质来源和Fe²⁺ 氧化沉淀机制两个方面,但都尚未达成共识。物质来源的观点主要有大陆风化剥蚀、海底热液、海底热液和海水的混合物、热液淋滤洋壳、既有大陆物质来源又有热液来源,沉淀机制主要有生物沉淀和非生物沉淀两种认识,前者是指Fe²⁺ 利用微生物（如蓝藻）光合作用产生的O₂氧化成Fe³⁺,或Fe²⁺ 直接被微生物代谢氧化,后者主要包括热液与海水混合、密度流作用、相分离、紫外线引起Fe²⁺ 氧化沉淀等。  相似文献   

河南省安林矽卡岩型铁矿的成岩时代和成矿物质来源探讨   总被引：4，自引：1，他引：3  

陈艳  张招崇  朱江 《岩石学报》2014,30(5):1307-1321

位于华北克拉通中部的河南省安林铁矿是典型的邯邢式矽卡岩型铁矿,矿体产于闪长质岩石和中奥陶统灰岩的接触带。LA-ICPMS锆石U-Pb定年结果表明安林闪长岩体的侵位年龄为123.38±0.81Ma,略晚于华北克拉通东部地区的含矿岩体,形成于岩石圈大规模减薄伸展时期。但其中含有古老的锆石说明岩浆经历了地壳的混染。闪长质岩石具有相对低SiO2、高Mg#、高碱,富集Ba、Sr和LREE大离子亲石元素,亏损Nb、Ti、Ta等高场强元素的特点,暗示了其形成于岩石圈地幔。岩相学特征以及Harker图解指示了岩浆经历了较强的分离结晶作用,因此推断安林闪长岩可能是软流圈地幔上涌导致富集的岩石圈地幔发生部分熔融形成原始的辉长质岩浆在上升过程中或岩浆房中发生了以铁镁矿物为主的分离结晶作用,同时受到地壳物质的混染的结果。安林地区矿石具有和闪长岩体相似的稀土元素地球化学特征,反映铁的成矿作用与岩浆作用密切相关。矿床中闪长岩体、矽卡岩、矿石和碳酸盐围岩的主量元素对比研究表明钠交代作用引起Na、K、Fe、Si等元素在各岩类间的迁移,其中迁移出的铁为成矿提供了物质基础。安林地区初始岩浆富含水,分离结晶作用使残留岩浆水饱和而发生出溶;且岩浆在演化过程中受到区内膏盐层和碳酸盐地层的混染,促进了岩浆中流体的出溶并使出溶的流体富含Cl-,为有利于铁质活化的富Cl-岩浆流体的形成创造了条件。  相似文献   

Molecular and stable carbon isotopic characterization of PAH contaminants at McMurdo Station, Antarctica     

Kim M  Kennicutt MC  Qian Y 《Marine pollution bulletin》2006,52(12):1585-1590

The molecular and stable carbon isotopic compositions of contaminant polycyclic aromatic hydrocarbons (PAHs) at McMurdo Station, Antarctica were analyzed in samples collected from land and sub-tidal area. PAHs in the study areas were characterized by high amounts of naphthalene and alkylated naphthalenes from petroleum products introduced by human activities in the area. Principal component analysis (PCA) of PAH composition data identified multiple sources of PAH contamination in the study area. Compositional assignments of origins were confirmed using compound specific stable carbon isotopic analysis.  相似文献   

Influence de l'hydrodynamique sur l'intrusion saline en aquifère karstique côtier     

Bruno Arfib  Thomas Cavalera  Eric Gilli 《Comptes Rendus Geoscience》2006,338(11):757-767

A new method of interpretation of the $Q\text{–}C$ hysteresis (discharge–salinity) during high water is proposed using the data recorded on coastal brackish karstic springs with salinity inversely proportional to the discharge. The method, based on the $Q_{\mathrm{mer}}\text{–}{C}_{\mathrm{T}}$ (seawater discharge–salinity) hysteresis, identifies the effect of the hydrodynamic changes on the flow and transport. Three phenomena are characterized: the emptying of the karstic conduit, the dilution by freshwater and the control of the seawater intrusion in the conduit by the hydraulic head variations. To cite this article: B. Arfib et al., C. R. Geoscience 338 (2006).  相似文献   

Geochemistry and Sm-Nd systematics of the 1.67 Ga Buanji Group of southwestern Tanzania: Paleo-weathering,provenance and paleo-tectonic setting implications     

Charles H. Kasanzu  Makenya A.H. Maboko  Shukrani Manya 《地学前缘(英文版)》2017,8(5):1025-1037

We present major and trace and Nd-isotopic data of the~1.67 Ga Buanji Group of southwestern Tanzania in order to constrain the nature of their protolith and the intensity of chemical weathering in the source terranes and make inferences on the nature of climatic conditions during the late Paleoproterozoic in the region. Major and trace element contents of the shales from three stratigraphic formations are comparable to those of the post-Archaean Australian Shale(PAAS) and the average Proterozoic Shale(PS). They are characterized by enrichments in LREE relative to HREE((La/Yb)_(CN)=9.07-13.2;(Gd/Yb)cN = 1.51-1.85) and negative Eu anomalies(Eu/Eu~* = 0.61-0.81); features which are comparable to those of PAAS and PS, indicating upper continental sources. Provenance proxy ratios,together with abundances of Cr, Ni, Co and V that increase up-stratigraphy suggest a decreasing input of felsic detritus up-stratigraphy. Chemical Indices of Alteration(CIA) for the lower, middle and upper Buanji formations are 81. 76 and 79, respectively. These indices largely indicate intermediate(ca. 60-80)to extreme(80) weathering intensities of the precursor rocks. These observations may suggest the prevalence of warm, humid climates during the late Paleoproterozoic in the region.The lower Buanji Formation yielded a depleted mantle Nd model age(T_(DM)) of 、2100 Ma which indicates an Eburnean parentage. T_(DM) ages of 2486-2155 Ma and 2535-2379 Ma obtained from middle and upper Buanji formations, respectively, suggest a progressive increase of sedimentary input from the Tanzania Craton up-stratigraphy. The Eburnean T_(DM) ages of the lower Buanji rocks are attributed to their derivation through denudation of a decaying topographic high composed predominantly of rocks that were generated during the Palaeoproterozoic Ubendian orogenesis, possibly in the realm of Columbian Supercontinent assembly. Overlapping T_(DM) ages between the middle and upper Buanji formations suggest multiple sources involving mixing of detritus from Archaean cratonic rocks and the Palaeoproterozoic Ubendian belt. However, the Archaean signal is relatively more pronounced in the upper Buanji Formation, suggesting sediments derivation from the craton, to the north of the basin. The middle Buanji Formation suggests more diverse protolith,given the relatively larger spread in the T_(DM) ages. The Nb/Ta, Zr/Sm and Ce/Pb ratios coupled with the negative Nb and Ta anomalies, relative to primitive mantle, suggest that the tectonic setting of the source rocks for the Buanji sediments was a subduction zone akin to that generating modern sland Arc Basalts. Thus, we suggest that the Buanji's palaeogeography is consistent with an extensional continental backarc basin during the late Paleoproterozoic.  相似文献   

Sedimentary evolution of overlapped sand bodies in terrestrial faulted lacustrine basin: Insights from 3D stratigraphic forward modeling     

《Marine and Petroleum Geology》2017

Terrestrial faulted lacustrine basins usually have large variabilities in structural subsidence and multiple river sources. The facies in such basins are thus characterised by frequently changed facies and complex relationship of overlapped sand bodies (e.g. Liaoxi Depression of Liaodong Bay, Bohai Sea, China). Therefore, it's a great challenge to quantitatively describe evolution of sand bodies and their overlap relationship. In this study a three-dimensional stratigraphic forward model is used to solve this problem, which is corrected according to well log data. After the parameter optimization was verified against borehole strata thickness and lithology, this model had a thickness error within 8%, and the lithology distribution agreed with the well data as a whole.Four evolution phases of the Shahejie 3 Formation were recognised through the modeling. In the first phase, the lake level rose, and the eastern fan delta sand developed. In the second phase, the fan delta sand scaled up, and the braided river delta front sand developed at a small scale. In the third phase, the lake level shifted from falling to rising, the fan delta sand further expanded the scale, and the braided river delta developed at a large scale. Sands on both sides overlapped at a large scale. In the fourth phase, the lake level rose, the lake basin expanded, and lake shale was the main lithology in the study area. From the sedimentary evolution of Es3 formation, sand overlapped in the third stage. In 39.75 Ma, two parts of the sand body began to overlap and reached largest scale in 39.6 Ma, which was approximately 10 km². Both then retrograded to a separation in 39 Ma when the overlap ended.Coupling stratigraphic forward simulation with uncertainty quantification allowed us to estimate the influence of each stratigraphic parameter on sand overlap. Fluvial discharge appears to be the most influential parameter while the initial bathymetry and lake level variations exert a minor to moderate impact.  相似文献   

Depositional environment and geochemical characteristics of the Lower Carboniferous source rocks in the Marsel area,Chu-Sarysu Basin,Southern Kazakhstan     

《Marine and Petroleum Geology》2017

There are two sets of carbonate source rocks in the Lower Carboniferous layers in Marsel: the Visean (C₁v) and Serpukhovian (C₁sr). However, their geochemical and geological characteristics have not been studied systematically. To assess the source rocks and reveal the hydrocarbon generation potential, the depositional paleoenvironment and distribution of C₁v and C₁sr source rocks were studied using total organic carbon (TOC) content, Rock-Eval pyrolysis and vitrinite reflectance (Ro) data, stable carbon isotope data, gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) analysis data. The data were then compared with well logging data to understand the distribution of high-quality source rocks. The data were also incorporated into basin models to reveal the burial and thermal histories and timing of hydrocarbon generation. The results illustrated that the average residual TOC contents of C₁v and C₁sr were 0.79% and 0.5%, respectively, which were higher than the threshold of effective carbonate source rocks. Dominated by type-III kerogen, the C₁v and C₁sr source rocks tended to be gas-bearing. The two source rocks were generally mature to highly mature; the average Ro was 1.51% and 1.23% in C₁v and C₁sr, respectively. The source rocks were deposited in strongly reducing to weakly oxidizing marine–terrigenous environments, with most organic material originating from higher terrigenous plants and a few aquatic organisms. During the Permian, the deep burial depth and high heat flow caused a quick and high maturation of the source rocks, which were subsequently uplifted and eroded, stopping the generation and expulsion of hydrocarbons in the C₁v and C₁sr source rocks. The initial TOC fitted by the △logR method was recovered, and it suggests that high-quality source rocks (TOC ≥ 1%) are mainly distributed in the northern and central local structural belt.  相似文献