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高校地质学报 ›› 2020, Vol. 26 ›› Issue (6): 628-638.DOI: 10.16108/j.issn1006-7493.2020004

• 岩石·矿物·地球化学 • 上一篇    下一篇

川南普格玄武岩中沥青质杏仁体的矿物学与成因

张良钜,阮青锋*,杨育富,李东升,曾伟来   

  1. 桂林理工大学 地球科学学院,桂林 541004
  • 出版日期:2020-12-20 发布日期:2021-01-05

Mineralogy and Genesis of Asphaltene Amygdalae in the Puge Basalt, Southern Sichuan, China

ZHANG Liangju,RUAN Qingfeng*,YANG Yufu,LI Dongsheng,ZENG Weilai   

  1. College of Earth Sciences, Guilin University of Technology, Guilin 541004, China
  • Online:2020-12-20 Published:2021-01-05

摘要: 川南普格玄武岩顶部发育了一系列杏仁体,沥青、绿泥石、石英、自然铜等矿物以各种产状出现在杏仁体中。系统的矿物学研究表明:杏仁体中的绿泥石为辉绿泥石,形成于中—高温富有机质成矿热液环境;沥青属于石油沥青,有机质来源于下伏地层的中二叠统阳新组(P2 y)生物碎屑灰岩;绿泥石、沥青、石英及自然铜等矿物是玄武岩成岩后的构造应力与晚期基性火山活动共同作用形成的含有机质成矿热液演化的结果,其形成过程为:玄武质岩浆末期(基性岩浆作用末期)→含铜的火山热液(火山热液作用)→构造应力→含有机质的成矿热液→绿泥石→第一世代沥青→乳白色石英→烟灰色石英、第二世代沥青、自然铜→辉铜矿→葡萄石。玄武岩中含沥青的杏仁体、晶洞以及构造破碎带可以作为该地区的铜矿化的重要找矿标志。

关键词: 沥青, 绿泥石, 玄武岩, 杏仁体, 川南普格

Abstract: A series of amygdalaes with asphalt, chlorite, quartz, native copper, occur in the Puge basalt, Southern Sichuan, China. The petrological and mineralogical features of different amygdalae were systematically studied by modern analytical techniques. The results show that chlorite in the amygdalae belongs to diabantite, formed in a medium-high temperature, organic-rich hydrothermal environment. Asphalt belongs to petroleum asphalt and was derived from bioclastic
limestone of the Middle Permian Yangxin Formation (P2 y). Chlorite, asphalt, quartz and native copper crystallized in the organic hydrothermal fluid, which are derived from late basic volcanic activity under the tectonic stress after the formation of basalt. A commonly recognized sequence of the processes for the formation of these amygd alaes can be summarized as follows: the later magma stage of Puge basalt → Cu-rich volcanic hydrothermal fluid→tectonic stress→organic ore-fluid →chlorite →the first generation of asphalt →white quartz → smoke-gray quartz, the second generation of asphalt, and native copper →chalcocite→prehnite. The asphaltene amygdalae, crystal cavities and tectonic fracture zone in the basalt can be regarded as important prospecting indicators for Cu mine ralization in the Emeishan Large Igneous Province.

Key words: asphalt, chlorite, basalt, amygdala, Puge, Souhtern Sichuan

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