摘要
对天等地区原生碳酸岩锰矿层以及矿层顶底板及矿层之间常见的有机质岩层岩芯样品进行了主元素、微量元素、稀土元素、有机质含量测定和生物标志物鉴定。分析结果表明,富有机质层主元素Fe/Ti-Al/(Al+Fe+Mn)、(Cu+Ni+Co)×10-Fe-Mn、Zn-Ni-Co、lgU-lgTh等图解,Co/Ni、U/Th、La/Ce等比值均表现出热水沉积环境的特点,Eu的正异常与弱的Ce正异常反映出还原性的沉积环境,其中6件硅质泥灰岩样品有机碳(TOC)丰度平均为1.41%,可溶有机质氯仿沥青"A"含量平均为0.034%;甾类、藿烷系列化合物分布特征与参数指示有机质处于高成熟演化阶段;正构烷烃、烷基环己烷和烷基环戊烷分布特征指示有机质来源主要为低等藻类。样品岩石学特征与主元素、微量元素、稀土元素及生物标志物特征表明,锰矿床形成受到热水作用与生物有机成矿作用的影响,锰质来源具有陆源-海生双源混入的特征,生物高生产率所造成的氧化还原环境变化促进了成矿。
The Dongping manganese deposit in the Tiandeng area is one of the most important manganese enrichment regions in southwestern Guangxi, The manganese deposit existed in the Beisi Formation siliceous marlstone of the Lower Triassic Series. However, less attention has been paid to this area, especially organic matter in the manganese-bearing rocks. On the basis of geological survey, we have carried out a study on the major elements, trace elements and rare-earth elements of 16 rock samples and the biomarkers of the rocks with high organic matter in the manganese-bearing rocks, further addressing the debated ore genesis in combination with regional geological characteristic features. Fe/Ti-A1/（AI＋Fe＋Mn）, （Cu＋Ni＋Co）×10-Fe-Mn, Zn-Ni-Co and lgU-lgTh diagrams, and Co/Ni, U/Th and La/Ce ratios show hydrothermal sedimentary characteristics. The bitumen of the high organic matter in the manganese-bearing rocks is 0.034% on average, and TOC is 1.41% on average. Distribution of hydrocarbons, alkylcyelohexane and alkylcyelopentane shows that the organic matter sourced from algae and microbenthos which played an important role in both bioorganic mineralization and mineralization. Based on the above results, it is proposed that the manganese deposit resulted from hydrothermal activities and bioorganic mineralization, and the manganese source was a mixed one of marine and terrigenous sources. High productivity caused redox environment changes, thus promoting mineralization.
出处
《地球化学》
CAS
CSCD
北大核心
2017年第1期46-65,共20页
Geochimica
基金
十二五国家科技支撑计划(2011BAB04B00)
关键词
下三叠统
北泗组
有机地球化学
生物标志物
热水沉积
东平锰矿
Lower Triassic Series
Beisi Formation
organic geochemistry
biomarker
hydrothermal sediment
Dongping manganese deposit
