高校地质学报Issue(4)：620-633,14.
皖南休宁蓝田剖面埃迪卡拉系皮园村组硅质岩的地球化学特征及成因
Geochemical Characteristics and Origin of Ediacaran Piyuancun Chert in the Lantian Section, Xiuning, Southern Anhui Province
摘要
Abstract
To determine the origin of silica in terminal Ediacaran chert, we have undertaken a variety of sedimentary geochemical proxies, in conjunction with geological features, on well-characterised Piyuancun chert at Lantian section from southern Anhui province. The Piyuancun cherts are typical marine siliceous deposits with microcrystalline structure and high content of SiO2. Silica constituting the chert is partially derived from submarine hydrothermal fluid, indicated by geochemical ratios of Fe/Ti>20 and Al/(Al+Fe)<0.4, as well as position in Al-Fe-Mn triangular diagram. However, Y/Ho ratios close to seawater from modern open sea and seawater-like rare earth element distribution patterns demonstrate that the sedimentary water body of Piyuancun chert primarily sourced from seawater. The isotope compositions of silicon and oxygen illustrate no variation trend stratigraphically whilst relatively high δ30Si values indicate that Piyuancun cherts were formed by chemical precipitation of dissolved silica from seawater rather than direct precipitation from hydrothermal fluid. Moreover, estimated values from oxygen isotopic geothermometer are also consistent with normal coeval seawater temperature. Bottom seawater was first mixed with silica-rich submarine hydrothermal fluid and subsequently driven by upwelling to relatively acidic waters far away from hydrothermal activity center. As a result, silica within the regional seawater became over-saturated and thus precipitated. Extensively existence of microfossils and algae mats including Palaeopascichnus jiumenensis in Piyuancun chert indicates the thriving ocean paleo-productivity. Acidic substance produced through degradation of organic matter and biodegradation process would have, to some extent, dropped the solubility of dissolved silica in seawater and thus promoted the deposition of Piyuancun chert.关键词
硅质岩/地球化学/皮园村组/埃迪卡拉系/皖南Key words
chert/geochemistry/piyuancun formation/ediacaran/southern Anhui province分类
天文与地球科学引用本文复制引用
何天辰,凌洪飞,陈永权,李达,杨爱华,王丹,吴赫嫔..皖南休宁蓝田剖面埃迪卡拉系皮园村组硅质岩的地球化学特征及成因[J].高校地质学报,2013,(4):620-633,14.基金项目
国家自然科学基金青年科学基金项目（41102018）；国家重点基础研究发展计划973项目（2013CB835000）联合资助 （）
