摘要
贵州天柱大河边早寒武世黑色岩系重晶石矿床在全球同类矿床中储量最大,是研究的热点,含矿岩系富有机质,但对其研究薄弱。本文对这些有机质新进行了系统的有机地球化学研究,并进一步结合其有机岩石学特征,研究讨论了尚存有争议的矿床成因。结果发现,成矿岩系中有机质含量丰富,有机碳含量最高可达8.3%,有机质母质主要来源于低等菌藻类,它们在成矿过程中发挥了重要作用;矿床形成于缺氧还原的海水环境,典型证据包括强烈的植烷优势,姥植比小于0.4,普遍检出四环萜烷与伽马蜡烷等;还受到热水作用影响,典型证据包括成矿岩系具有较高的沥青反射率,矿层比与围岩的有机质含量低,以及矿层干酪根同位素组成高于围岩等。据此,提出矿床经历了热水喷流与生物有机质的共同作用,建立了成矿新模式。这些认识还可望对其他沉积岩型矿床研究提供一定启示。
The Tianzhu Dahebian barite deposits are hosted in the Early Cambrian black shales of Guizhou Province, South China. They have the largest reserve within the same type of deposits all over the world, and thus become one of the research highlights in this field. Such deposits are rich in organic matter. However, less attention has been paid to organic matter in the deposits. Therefore, we carry out an organic geochemical study in this paper, and further address the debated ore genesis combined with organic petrological characteristics. The results show that the barite ore-bearing strata are rich in organic matter as total organic carbon content reaches up to 8.3%. The bio-precursor comes mainly from bacteria and algae, which have played an important role on the mineralization. The deposit was formed in an anoxic and reducing marine environment. Typical evidences include strong phytane advantage with Pr/Ph 〈 0.4 and wide detection of tetracyclic terpanes and gammacerane. On the other hand, the ore formation was influenced by hydrothermal water. Typical evidences include high bitumen reflectance for the ore bed, lower total organic carbon（TOC） and heavier kerogenδ13C valuesin the ore bed relative to those in the surrounding rocks. Based on the aboveresults, we propose the ore deposit suffered from the interaction of hydrothermal water with biological organic matter, and then establish a new mineralization model. These findings may also have additional implications for the study of other sedimentary-hosted deposits.
出处
《地球化学》
CAS
CSCD
2014年第4期386-398,共13页
Geochimica
基金
国家自然科学基金(40638042
41373044)
教育部博士点基金(20130091130007)
南京大学内生金属矿床成矿机制研究国家重点实验室自主课题(ZZKT-201308)
关键词
重晶石矿床
有机地球化学
黑色岩系
早寒武世
天柱
华南
barite deposit organic geochemistry black shales Early Cambrian Tianzhu County South China
