Organic geochemistry and hydrocarbon potential of source rocks from the Mohe Formation of the Upper Jurassic in the Mohe Basin, northeast China

Zhong-Ying Miao,Qing-Xia Xu 한국지질과학협의회 2017 Geosciences Journal Vol.21 No.3

The Mohe Formation is one of the important source rocks for oil-gas and gas hydrates in the Mohe Basin. In this paper, mudstone from cores of the M-1 and M-3 wells and argillite from cores of the MK-2 well of the Mohe Basin were studied. The depositional environment, organic matter source, thermal maturity, kerogen type, and hydrocarbon generation potential of the core samples were determined using organic and inorganic geochemistry. The dual sources of organic matter were terrestrial plants and aquatic organisms. The organic matter was deposited in a reducing lacustrine environment. The lake water salinity was higher when argillite was deposited. The late stage of the sedimentary filling of the lacustrine basin was characterized by high sulfate contents. The source rocks primarily contained Type II2–III kerogen. The present-day thermal maturity parameters reveal that the organic matter of the Mohe Formation is mature to overmature, indicating that this unit is capable of generating gas condensate and dry gas. In addition, we compared the organic geochemistry characteristics of mudstone and argillite. The results indicate that TOC, S1 + S2, and HI are lower in argillite than in mudstone. Although the biomarker maturity parameters cannot reflect the thermal evolution of the source rocks, they reflect the source of the organic matter and the depositional environment. The results provide important constraints for the evaluation of the hydrocarbon potential of lacustrine source rocks of the Mohe Formation from the Upper Jurassic and for the location of petroleum resources in the Mohe Basin.

하안단구 퇴적층의 지구화학적 특성과 기원지 - 단양천, 금천 유역을 대상으로 -

박충선,조영동,이광률 한국지형학회 2019 한국지형학회지 Vol.26 No.1

This study tries to reveal source areas of fluvial terrace deposits in Danyang and Geum River basins located in the northern and southern parts of the Sobaek Mountains, respectively, through geochemistry. The samples analyzed in this study show different grain size properties and can be grouped into the coarse, medium and fine samples. Grain size properties suggest that the coarse samples are typically fluvial deposits and geochemistry from the coarse samples is also similar to that from the bedrocks within the basins. The fine samples show geochemical properties different from the bedrocks and similar to loess deposits in Korea. However, different geochemical concentrations among the fine samples can be also recognized, indicating mixtures of loess materials with weathering products of the bedrocks. One sample among the medium samples is considered as fluvial deposit due to geochemical similarity to the bedrocks, while geochemistry from another sample among the medium samples indicates that loess materials were mixed with more abundant weathering products of the bedrocks than those in the fine samples.

남서태평양 라우분지 푸누아레이 열곡확장대 인근 퇴적물의 기원과 열수 분출의 증거

김문기,형기성,서인아,유찬민 한국해양과학기술원 2020 Ocean and Polar Research Vol.42 No.1

The bulk and partition geochemistry was studied in two sediment cores collected from the axial valley of the north-central Fonualei Rift and Spreading Center (FRSC), Lau back-arc Basin, southwest Pacific. The sediments consist of mostly volcanic ash, although minor amounts of biogenic and other components were present in some intervals. The major element composition of bulk sediments recalculated to a carbonate-free basis was in good agreement with the magma compositions of the adjacent Tofua Arc and the FRSC, with only significant difference in Mn content. The enrichment of Mn and other associated elements (e.g. Cu, Co, Ni, and P) is attributed to hydrothermal input to the sediments, as evidenced by their significant partitioning in the non-detrital phases according to the partition geochemistry. Hydrogenetic and diagenetic inputs were assessed to be relatively insignificant. Estimated hydrothermal Mn fluxes during the Holocene ranged between 5.0 and 37.1 mg cm-2 kyr-1, with the higher values in younger sediments, suggesting enhanced hydrothermal activity. The hydrothermal Mn fluxes comparable to or higher than those reported from other spreading centers with strong hydrothermal activities may indicate the presence of unknown hydrothermal vent sites and/or topographic restriction on the dispersal of hydrothermal plumes in the northern part of the FRSC.

La-Ce 및 Sm-Nd 동위원소계 측정을 위한 란탄-레진법과 HIBA(Hydroxy Isobutyric Acid)분리법의 상호비교

이승구(Seung-Gu Lee),이효민(Hyomin Lee),Yoshihiro Asahara,이미정(Mi-Jeong Lee),추미경(MiKyeong Choo),이승렬(SeungRyeol Lee) 한국암석학회 2012 암석학회지 Vol.21 No.4

원소의 고순도분리는 동위원소계 연구의 기초가 된다. 이 기술보고에서는 Sm-Nd 연대측정법에 중요한 원소군인 Sm과 Nd의 원소분리에 자주 이용되고 있는 HDEHP를 이용한 테플론분말(란탄-레진)법과 Sm-Nd 동위원소계 및 La-Ce 동위원소계의 연구를 위한 원소분리법인 α-HIBA(α-Hydroxy Isobutyric acid)법의 장단점을 한국지질자원연구원(KIGAM), 기초과학지원연구원(KBSI), 극지연구소(KOPRI) 및 일본 나고야대학과 같은 각 기관별 용리곡선을 통해 비교 소개하였다. 동위원소 지구화학연구를 위한 이 고순도의 원소분리법 비교는 Sm-Nd계 및 La-Ce계 동위원소 지구화학연구자의 실험법 선택에 많은 도움을 줄 것이다. A column chemistry is the most useful tools for isolating the elements of interest in isotope geochemistry. Here we introduce the chemical experimental procedure for Sm, Nd, La and Ce separation such as Teflon powder or Ln-resin method using HDEHP of KIGAM, KBSI, KOPRI and α-HIBA(α- Hydroxy Isobutyric acid) method of Nagoya University, Japan. This technical report will provide an useful information in selecting the experiment method for rare earth element isotope system study such as Sm- Nd and La-Ce isotope system.

충남 금산군 일대 지하수내 비소의 지구화학적 분포

안주성,고경석 한국자원공학회 2008 한국자원공학회지 Vol.45 No.5

Groundwaters for potable and agricultural uses in the Geumsan area have been surveyed to investigate the occurrence of As and its geochemistry. Among 150 samples, 16 percent of groundwaters had concentrations greater than 10 µg/L rising up to 113 µg/L. Simple Ca-HCO3- types without external pollution and general positive correlations with pH, Ca, SO42- and HCO3- were characteristics of high As (≥10 µg/L) groundwaters. Geochemical parameters such as pH, F, SO42-, HCO3-, Ca, and Mg, showed differences between geological media in contrast to As of narrow variation in contents. This may indicate that As occurrence is more affected by local hydrogeochemical conditions rather than the contents in aquifers. The oxidation reaction of sulfide minerals in metasedimentary rocks and locally mineralized zones seems to be ultimately responsible for the existence of As in groundwater. Desorption process under high pH conditions may also control the As mobility in the study area.

울주군 사연댐 건설 전후의 퇴적지화학적 환경 변화

오강호,고영구,류춘길 한국도서(섬)학회 2019 韓國島嶼硏究 Vol.31 No.4

This study focuses on the geochemical characteristics on deposits around the Sayeon-Dam in the scope of sedimentary geochemistry. The deposits are composed of sediments formed before/after the building of the Sayeon-dam. The sediments around the dam are reasonable for environmental changes influenced by industrialization in 1960’s. Sedimentary environments and geochemical characteristics were changed one after another in the time of and after the dam construction. Firstly, the mean grain size had a fining tendency of 2.93 to 4.95Ø in the sediments. Next, elements of Al, Fe, Mg, P, Co, Cr, Cu, Zn, Pb, Cd in the sediments increased in contents with rises of TOC and TC, and other organic components. Before the dam construction, in the sediments, C/N ratios of 0~13.50(avg. 5.50) indicated a hydrophyte dominated condition. However, the conditions were changed into a land plant dominated one as the ratio changes of 0.01~23.21(avg. 10.52) after the dam construction. Showing a positive correlation of above 0.9 between the values of Al, Fe, Mg, Ca, P, Co, Cr, Cu, Zn, Pb, TC, and grain size fining before the dam’s construction, the relationships decreased after the building. In addition, enrichment factors(EF) of Cu, Zn, and Pb were enhanced after the building. Before the building, controlling factors of the sediments had a loading of 61.610 % by surrounding natural and geological settings in the factor analysis. However, after the building, the loading decrease of 41.811% and the factors were dispersed. From the above results, it is indicated that the sediments were influenced by grain size fining, a change into lacustrine environment, and artificial interpretations in geochemical behavior. 이 연구는 사연호 주변의 퇴적층 조사를 통한 지화학적 특성을 분석한 것이다. 연구지역은 1960년대 공업용수와 인근 지역 주민의 생활용수를 공급하기 위하여 사연댐을 건설하였다. 연구 지역은 반구대 암각화가 있는 하천의 건너편 지역으로 주변 퇴적층은 사연댐이 건설되기 이전의 퇴적층과 이후의 퇴적층이 분포하고 있다. 이 지역은 인간이 인위적 건설로 인한 퇴적층의 환경변화를 간직한 곳으로 산업화에 의한 1960년대 전후의 환경변화를 살펴볼 수 있는 중요한 곳이다. 이 연구는 사연댐 건설 전후의 하천환경 변화를 퇴적물의 지화학 분석을 통해 고찰한 것으로 하천환경의 변화와 함께 댐 건설과 같은 인위적 영향을 파악하는데 목적이 있다. 사연댐 건설 전후의 퇴적환경과 지구화학적 특성은 건설 전과 후의 환경 변화가 인지된다. 퇴적물의 평균입도는 평균 2.93Ø에서 4.95Ø로 세립화 되어진다. 지화학적 성분인 Al, Fe, Mg, P, Co, Cr, Cu, Zn, Pb, Cd 등의 평균 함량이 증가하는 경향이 뚜렷하며, 유기지화학 성분인 TOC, TC도 증가하고 있다. 사연댐 건설 이전 퇴적층에서 C/N 비는 0.00~13.50(평균 5.50)으로 수생식물과 육상식물 기원의 유기물들이 혼합된 것으로 보이며, 수생식물이 우세한 환경이었을 것으로 추정된다. 사연댐 건설 이후의 퇴적층에서 C/N 비는 0.01~23.21(평균 10.52)로 수생식물과 육상식물 유기물들이 혼합되어 있으며, 상대적으로 육상식물이 우세한 환경으로 추정된다. 지화학적 원소들의 특성은 퇴적층 내에서 원소들 간의 상관성, 부화지수, 거동특성, 평균함량 비교 등을 통해 알 수 있다. 사연댐 건설 이전의 퇴적층에서 지화학적 원소들은 평균입도와 관련한 Al, Fe, Mg, Ca, P, Co, Cr, Cu, Zn, Pb TC 등이 0.9 이상의 정(+)의 상관관계로 입도가 세립해질수록 함량이 증가하는 경향을 강하다. 사연댐 건설 이후의 퇴적층에서는 입도와 상관관계가 낮은 것으로 나타났다. 원소들의 상대적인 농축정도를 파악하기 위한 부화지수는 사연댐 건설 이후의 퇴적층에서 유해 중금속에 해당하는 Cu, Zn, Pb 등의 부화지수가 크게 변화하며 높아지는 경향을 보인다. 사연댐 건설 이전 퇴적물 내의 원소들의 거동에 영향을 주는 요인들은 주변 지질 및 자연환경적 영향에 의한 61.610% 적재량을 보이나, 건설 이후에는 41.811%로 떨어지고, 요인들이 분산되는 경향이 강하다. 이는 사연댐 건설 이전의 자연 환경과 달리, 건설 이후의 지화학적 환경은 주변 지질 영향 외에도 퇴적물의 세립화, 호소환경으로 변화, 인간의 인위적 영향 등이 복합적으로 작용하고 있음을 강하게 시사한다.

Geochemistry of Miocene sedimentary rocks from offshore West Baram Delta, Sarawak Basin, Malaysia, South China Sea: implications for weathering, provenance, tectonic setting, paleoclimate and paleoenvironment of deposition

Joel Ben-Awuah,Eswaran Padmanabhan,Rajalingam Sokkalingam 한국지질과학협의회 2017 Geosciences Journal Vol.21 No.2

Geochemistry, paleoweathering, provenance, tectonic setting, paleoclimate and paleoenvironment of deposition of offshore Miocene sedimentary rocks in the West Baram Delta have been examined through multi-element geochemistry and mineralogy. Materials and methods used in the study include ninety four core samples from four subsurface wells, XRF, thin sections and FESEM. Four main groups of samples are identified in the wells: porous sandstones, cemented sandstones, siltstones and mudstones. The sandstones are classified as sublitharenites, litharenites and Fe-rich sandstones based on chemical composition and mineralogy. Variations in compositional trends suggest strong lithological and diagenetic controls on the geochemical composition of the samples. Petrography of the samples indicates that they are composed mainly of quartz, K-feldspar, siderite and clay minerals. The samples are characterized by moderate to high degree of chemical weathering with CIA values between 52–76 and PIA values from 65–100. Provenance analysis of the samples shows predominantly felsic and intermediate igneous provenance with minor mafic contribution. The samples are inferred to have originated from a passive margin tectonic setting that followed the continental collision and rifting stages of the foreland basin development phase of the Sarawak Basin. The paleoclimate of deposition of the samples is interpreted to be warm and humid enhancing the chemical weathering. The paleoenvironment of deposition is predominantly suboxic to anoxic.

Geochemistry of Çamardl Formation sediments, central Anatolia (Turkey): implication of source area weathering, provenance, and tectonic setting

Seref Keskin 한국지질과학협의회 2011 Geosciences Journal Vol.15 No.2

The upper Cretaceous-Eocene ‚amardl Formation is exposed along the northern edge of the Ulukl la Basin (central Anatolia) and consists of turbiditic sediments. The sediment geochemistry has been studied in order to understand the provenance, source area weathering, and tectonic setting of the basin. ‚amardl Formation sediments are characterized by low to moderate SiO_2 contents, variable abundances of major elements, and a relatively high proportion of ferromagnesian elements. Evidence from discrimination diagrams of sedimentary provenance, tectonic setting, major element geochemistry and Sc/Th, Cr/Th, Co/Th, Zr/Sc, La/Sc, La/Co, Cr/Sc, Y/Ni, and K/Rb values show that the ‚amardl Formation sediments were derived from mafic, felsic, and intermediate sources. The chemical index of alteration (CIA: 57.63–78.11) revealed moderately weathered source rocks. Then major and trace element concentrations indicated deposition in an active continental margin and continental island arc settings.

Sphalerite geochemistry of the Zn-Pb orebodies in the Taebaeksan metallogenic province, Korea

Lee, Jun Hee,Yoo, Bong Chul,Yang, Yun-Seok,Lee, Tong Ha,Seo, Jung Hun Elsevier 2019 Ore geology reviews Vol.107 No.-

<P><B>Abstract</B></P> <P>The Taebaeksan region, located in the northeastern part of South Korea, is an important metallogenic province which hosts numerous Zn-Pb-W-Mo-Fe-Cu (-Au-Ag) mineral systems. The Zn-Pb orebodies in the region (inclusive of skarn, carbonate replacement, and vein-breccia ore types) are hosted on the early Paleozoic carbonate sequences and they are associated with late Cretaceous to early Paleogene magmatic-hydrothermal activities. We collected Zn-Pb orebodies from 15 areas including non-metal deposits, such as high-Ca calcite marble, as well as exploration sites in the Taebaeksan metallogenic province. Thereafter, we studied the geochemistry of the sphalerite present in them to understand the regional Zn-Pb mineralization process and to establish an exploration strategy.</P> <P>The sphalerites collected from the region contained detectable amounts of Fe, Mn, Cd, Co, Cu, Ga, Ge, Mo, Ag, In, Sn, Sb, W, Tl, Pb, and Bi which were identified using microbeam techniques like EPMA and LA-ICP-MS. Sphalerites from economically significant Zn-Pb deposits characteristically have high Mn and low Cd content, while W (-Mo)-bearing deposits have remarkably high Cd content. Correlation trends between trace elements demonstrate the coupled substitution mechanisms such as 3 Zn<SUP>2+</SUP> ↔ 2 (Cu<SUP>+</SUP> or Ag<SUP>+</SUP>) + Sn<SUP>4+</SUP> and 2 Zn<SUP>2+</SUP> ↔ Cu<SUP>+</SUP> + In<SUP>3+</SUP>, occurring in the sphalerite. High-temperature ores such as skarn and vein-breccia are relatively enriched with Co and In, while Ga, Ag, and Sn tend to be concentrated in the relatively low-temperature ores, such as carbonate replacement type ores.</P> <P>Lead isotope compositions of the sphalerites show a well-defined, positive, linear trend with those of the local Cretaceous intrusions and the sedimentary sequence of the Taebaeksan region. Major economic Zn-Pb deposits show relatively more signatures of non-radiogenic Pb isotope closer to the intrusions, as compared to the minor and sub-economic Zn-Pb orebodies. The Pb isotope signature suggests that Cretaceous magmatic-hydrothermal fluids with a minimal degree of fluid-rock interactions are required for economic Zn-Pb mineralization in the Taebaeksan metallogenic province.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The Zn-Pb orebodies in the Taebaeksan region were formed by magmatic-hydrothermal activities. </LI> <LI> Economic Zn-Pb mineralization is associated with minimal fluid-rock interaction. </LI> <LI> Trace elements in sphalerites show a temperature-dependent systematic trend. </LI> <LI> Geochemistry of the sphalerite provides insights regarding hidden Zn-Pb orebody. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Geochemistry of Neoproterozoic limestones of the Shahabad Formation, Bhima Basin, Karnataka, southern India

Ramasamy Nagarajan,Jayagopal Madhavaraju,John S. Armstrong-Altrin,Raghavendra Nagendra 한국지질과학협의회 2011 Geosciences Journal Vol.15 No.1

Major, trace and rare earth element (REE) geochemistry of carbonate rocks of the Neoproterozoic Shahabad Formation, southern India were studied in order to investigate the depositional environment and source for the REEs. The PAAS (Post Archaean Australian Shale) normalized REE + Y pattern of Shahabad limestones have consistent seawater-like pattern i.e., i) LREE depletion (average (Nd/Yb)_(SN) = 0.64 ± 0.08), ii) negative Ce anomaly, iii) positive Gd anomaly (average Gd_(SN)/Gd^* = 1.05 ± 0.16), iv) superchondritic Y/Ho ratio (average Y/Ho = 38.13 ± 21.35). The depletion of LREE and enrichment of HREE are clearly indicated by the (La/Yb)_(SN), (Dy/Yb)_(SN) and (Nd/Yb)_(SN) ratios, which suggest the retention of seawater characteristics in these limestones. The negative Ce anomaly reflects the incorporation of REE directly from seawater or from the pore water under oxic condition, and also reveals the mixing of two-component systems with terrigenous clay (detrital) in the marine sediments. The terrigenous input in these limestones is confirmed by positive correlation of REE with Al_2O_3, negative correlation of REE with CaO and differences in Y/Ho ratios. V, Cr, and Sc, are positively correlated with Ti, and strong positive correlation of REE with Fe_2O_3, Ni, Cr, Sc, and Y also indicate the presence of terrigenous materials in the Shahabad limestones.