| 磷矿的形成与Rodinia超大陆裂解、生物爆发的关系-以贵州瓮安、开阳、织金磷矿床为例 |
| 其他题名 | Formation of phosphorite deposit, Breakup of Rodinia supercontinent and Biology explosion-Acase study of Weng'an, Kaiyang and Zhijin phosphorite deposits of Guizhou Province
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| 施春华
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| 学位类型 | 博士
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| 2005
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| 学位授予单位 | 中国科学院地球化学研究所
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| 学位授予地点 | 中国科学院地球化学研究所
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| 学位名称 | 博士
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| 学位专业 | 地球化学
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| 关键词 | 贵州
陡山沱组
寒武纪
磷矿床
Redinia超大陆裂解
生物爆发
热水沉积
生物成矿
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| 摘要 | 贵州省分布有两期大型磷矿：震旦纪陡山沱期和早寒武纪梅树村时期。在这两期磷矿中分别发育有瓮安生物群和小壳动物梅树村生物群，这两个生物群代表了生命早期演化过程中的两次爆发事件。由此推测磷矿的形成可能与生物的爆发存在某种联系。另外，已有研究表明，磷矿层下伏的南沱冰碳岩和上覆的灯影帽碳酸盐的形成都与晚元古代末的Rodini。超大陆裂解相关，那么沉积于它们之间的磷矿也可能与Rodinia超大陆裂解相关联。研究磷矿形成、Rodinia超大陆裂解及生物爆发三者之间的关系对揭示磷矿的物质来源、成矿环境、构造条件、成因机制等有重要的理论意义；对解决全球范围晚元古代地层、几次生物爆发事件和．冰川事件的对比问题等有极其重要的理论和实际意义。本文以晚元古代陡山沱期（瓮安、开阳）和早寒武纪（织金）磷矿床为研究对象，借鉴岩相学、古生物学、元素地球化学、同位素地球化学、有机地球化学及Sm-Nd、Rb-Sr同位素定年等方法，讨论磷矿的形成与Rodini。超大陆裂解、生物爆发之间的关系。论文主要获得了以下几个方面的认识：研究了三个矿床的主要地质特征，表明寒武纪织金磷矿床的磷品位低于陡山沱期磷矿床。瓮安、织金磷矿床形成于氧化带环境，而开阳磷矿床形成于亚氧化带环境。确定了三个矿床的成矿时代。同位素年代学得出陡山沱组磷矿床形成年龄为583±19Ma（Sm-Nd法）、588±8.6Ma和582±7.7Ma（Rb-Sr法），寒武纪磷矿床的形成年龄为542±23Ma（Sm-Nd法）和541±12Ma（Rb-Sr法）。震旦纪陡山沱期和寒武纪梅树村期磷矿床的形成时代与华南地块从Rodinia超大陆中裂解漂移出来的时间（600Ma～550Ma、540Ma）相耦合，为Rodinia超大陆裂解事件与磷矿床的形成存在密切成因联系提供了年代学方面的证据。对三个磷矿床进行的大量地质地球化学研究表明：Rodinia超大陆裂解为磷矿的形成提供了热液源和慢源成矿物质，并造成了大规模的低温热液成矿作用。研究了发育于陡山沱组和寒武纪含磷地层中的瓮安生物群和梅树村小壳生物群爆发的原因，表明Rodini。超大陆裂解造成了两次生物大爆发。超大陆裂解引发地球化学异常，导致了生物的大发展。讨论了地层中生物与磷的关系。地质证据、伴生微量元素证据、磷灰石矿物地球化学证据及有机地球化学证据表明，生物有机质直接或间接地参与了成磷作用。其中生物直接参与成磷作用主要发生在成矿过程的磷质吸取阶段，同时也见于地球化学富集阶段还原型细菌活跃的成岩带中；有机质间接成磷作用主要发生在磷块岩成矿过程的地球化学富集阶段和物理富集阶段。总结了磷矿的形成与Rodinia超大陆裂解、生物爆发之间的关系，Rodinia超大陆裂解为磷矿的形成提供了热液源和慢源的成矿物质；同时引发了生物的大爆发，而生物大爆发则促进了成矿物质的超常聚集和大规模成矿。 |
| 其他摘要 | Guizhou Province is rich in phosphorite resource, which was formed in the Doushantuoan of the Late Sinian and the Meishucunian of the Early Cambrian. The two stages phosphorit preserved the earliest Weng'an biota and Meishucun biota respectively. The two biotas are representative of two biology explosion events during the early evolvement of life. Based on the above, we may confer that there lie relationship between the formation of phosphorite and the biology explosion. In addition, studying indicate that the tillite of Nantuo Fm. and the "cap" carbonate of Dengying Fm. have relationships with the breakup of Rodinia supercontinent. The phosphorite deposited underlying Dengying carbonate and overlying Noutuo tillite, so the formation of phosphorite also has relationship with the breakup of Rodinia supercontinent. To study the relationships of the formation of phosphorite, the breakup of Rodinia supercontinent and the biology explosion is significant not only for revealing the source, environment, structure and mechanism of the deposit but also for resolving the problem to contrast Neoproterozoic strata, the events of several biology explosions and of glaciations world-wide. Analyses of petrography, paleontology, elemental-chemistry, isotopic geochemistry, organic geochemistry and isotope chronology are conducted on phosphorite of Doushantuo Formation and Early Cambrian from Weng'an, Kaiyang and Zhijing deposit in Guizhou province, SW China. The purpose of this study is to advance our understanding of the relationships of the formation of phosphorite, the breakup of Rodinia supercontinent and the biology explosion by documenting and interpreting the geochemistry of the phosphorites. The studying gets some conclusions as follows: Study of the geology of three phosphorites indicate that the phosphorite of Doushantuoan is richer in P than that of Cambrian. The Weng'an and Zhijin deposited oil the oxidation zone, and the Kaiyang phosphorite deposited on the suboxidation zone. The mineralogenetic epoch of three phosphorites have been gained. The isochron age of the Doushantuoan phosphorite deposit is about 583±19Ma (Sm-Nd dating) and 588±8.6Ma, 582±7.7Ma (Rb-Sr dating). The isochron age of the Cambrian Meishucunian phosphorite deposit is about 542±23Ma(Sm-Nd dating) and 541±12Ma(Rb-Sr dating). These ages are coupled of that (600Ma-550Ma, 540Ma) of the breakup of South China block from the Rodinia supercontinent. So it gives a chronological proof to support the view that the breakup of Rodinia supercontinent is responsible for the formation of phosphorite. The contents of the ore-forming elements, trace element, rare earth elements and the isotopic compositions of Nd indicate that the breakup of Rodinia supercontinent provide hydrotliermal and mantle's ore material for the phosphorite and lead to hypothermia metallogenesis in large-scale. Investigating the Weng'an biota in the Doushantuo stratum and the small-shell biota in the Cambrian stratum, suggest that the breakup of Rodinia supercontinent is responsible for these two biology explosions. The relations of biology and P in the stratum indicate that biology participated in phosphatization directly or indirectly. There are several proofs: geology, trace element, apatite mineral geochemistry and organic geochemistry. The biology participated in phosphatization directly mainly occurred f during the process of assimilating P. Then the indirectly phosphatization occurred during the process of geochemical and physical enrichment. In conclusion, the breakup of Rodinia supercontinent initiated the biology explosion, and provided the hydrothermal and mantle's ore material. The biology enriched and accumulate P element and further formed the phosphorite. |
| 页数 | 108
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| 语种 | 中文
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| 文献类型 | 学位论文
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| 条目标识符 | http://ir.gyig.ac.cn/handle/352002/3712
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| 专题 | 研究生_研究生_学位论文
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推荐引用方式
GB/T 7714 |
施春华. 磷矿的形成与Rodinia超大陆裂解、生物爆发的关系-以贵州瓮安、开阳、织金磷矿床为例[D]. 中国科学院地球化学研究所. 中国科学院地球化学研究所,2005.
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