| 湘西下寒武统有机地化特征--MVT铅锌矿床有机成矿作用研究(Ⅲ) |
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| 引用本文： | 刘文均,卢家烂.湘西下寒武统有机地化特征--MVT铅锌矿床有机成矿作用研究(Ⅲ)[J].沉积学报,2000,18(2):290-296. |
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| 作者姓名： | 刘文均 卢家烂 |
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| 作者单位： | 1 成都理工学院 成都 610059; |
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| 摘 要： | 研究了湘西黔东地区下寒武统有机地球化学特征,包括三个富含有机质的层位 :底部牛蹄塘组黑色页岩;清虚洞组下部泥质条带灰岩和中部泥质灰岩,其中的泥质灰岩层是花垣MVT铅锌矿床的矿化围岩之一。这些层位中有机质的正构烷烃、类异戊二烯烃类、甾烷和萜烷的生物标志化合物特征表明,它们的先质来源与寒武纪海中的菌藻类有关。这些有机质都具有较高的演化程度,均已进入生油门限,以黑色页岩的演化程度最高,但仍未达演化的终点阶段。泥质岩的演化程度不仅与成岩作用有关,而且受到成矿热流体的影响,造成有机质的族组成、生物标志化合物和最高热解温度 (Tmax)等与矿化强度成正比关系的变化。部分烃类可能还直接参与了成矿作用。
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| 关 键 词： | 有机质 热演化程度 成矿作用 |
| 收稿时间： | 1998-11-04 |
Characteristics of Organic Geochemistry of Lower Cambrian in West ern Hunan--Organic-mineralization study on MVT Lead-Zinc ore deposits |
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| LIU Wen-jun,LU Jia-lan.Characteristics of Organic Geochemistry of Lower Cambrian in West ern Hunan--Organic-mineralization study on MVT Lead-Zinc ore deposits[J].Acta Sedimentologica Sinica,2000,18(2):290-296. |
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| Authors: | LIU Wen-jun LU Jia-lan |
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| Institution: | 1 Chengdu Institute of Technology Chengdu 610059;2 Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640 |
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| Abstract: | The paper have studied the characteristics of organic geochimestry of Low er Cambrian and relavant mineralization of Lead-Zinc ore deposits in western Hu nan and eastern Guizhou province.The lower Cambrian is located at the passive co ntinental margin of Yangtze landmass in southeast,and divided into three units f rom lower to upper,i.e.,Niutitang Formation,Balong Formation and Qingxudong Form ation,which belong to basin,shelf and ramp to margin reef-band facies of carbon ate platform respectively.Algal limestone,grey-dark muddy limestone and overlyin g oolite limestone are host rocks of Huayuan MVT Lead-Zinc ore deposits in Qingx udong Formation. There are three beds richin organic matter:black shale in lower part of Ni utitang Formation,zebra muddy limestone in lower part and grey-dark muddy limes ton in middle part of Qingxudong Formation,and the black shale is much higher (75%) than other beds (0.2%～0.4%).On the basis of the GC-MS of organic matter t racts and Rock-Eval Py,Py-GC analysis,their characteristics of normal paraffin i s higher carbon number range,single peak at the back,higher carbon number of mai n peak (27～31),weak odd-even predominance,and Pr/Ph＜1，but the charact eristics of biomarker of sterane and terpane are different between them.Ischoles tane is predominant in sterane of black shale(C29 is main(=34.33%),C29 αββ/ααα=2.18) and in grey-dark muddy limestone,cholestane is predominant (C29=42.2%,C29αββ/ααα=0.42).Tricycline terpane is predomenant in terpane of black shale(65.65%),Tm/Ts=1.14,and in grey-dark muddy limestone,ho pane is predominant(=66.2%),Tm/Ts=1.22.Above mentioned characteristics suggest t hat the precursor origin of organic matter among all beds is blue algal and bact eria in Cambrian sea,and deposited on the reduction to weakly redaction environm ents.The evolution level of organic matter is different among them,they have pas sed oil-window and the black shale is higher than other,but it is still not beyo nd the end stage of evolution. Some data evidence that the evolution level of altered grey-dark muddy limestone is not only related to diagenisis but also to hot ore-forming fluid.Therefore,they can result in obvious change of group composits,biomarker,pyrolysis T WTBZ〗maxand pyrolysis parameters.In massive muddy limestone,chloroform bit umen “A”=0.004%,saturated hydrocarbon=11.80%～41.1%，aromatic hydrocarbon=15.0 7% ～5.45%,asphaltene=31.00%～50.94%,Zn＜0.1%,but in interbedded rocks,Zn＞1.0%, chloroform bitumen “A”increased to 0.0112%,saturated hydrocarbon rise to 42.18 %～57.06%,aromatic hydrocarbon to 9.7%～21.47%,and asphaltene decrease to 7.36% ～14.55%,pyrolysis Tmaxfrom massive rock's 397℃ increase to interbedded rock's 510℃,and with increase of mineralization there occur the decrease in free hydrocarbon (S1),pyrolysis hydrocarbon (S2),hydrogen index (HI),oxygen index (OI) and hydrocarbon index (S1/TOC) of grey-dark muddy lime stone,All these suggest that there are close relationship between the organic co mposition and mineralization,and some organic composition may be directly precipitate during mineralization. |
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| Keywords: | organic matter evolution level mineralization |
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