重庆南川铝土矿物源分析:碎屑锆石U- Pb定年、Hf同位素和锆石微量元素示踪
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本文为国家重点研发计划项目(编号2017YFC0602701)和中国地质调查局项目(编号DD20160056、DD20160346、DD20190379)资助的成果。


Provenance of bauxite deposits in the Nanchuan district, Chongqing: evidence from U- Pb dating, Hf isotopes and trace elements in detrital zircons
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    摘要:

    重庆南川沉积型铝土矿主产于中下志留统韩家店组与中二叠统梁山组的侵蚀面上,即赋矿层位为梁山组中下部(大竹园组),是黔北- 渝南铝土成矿带的重要组成部分。铝土矿中碎屑锆石丰富,具有典型振荡环带特征,应用LA- (MC)- ICP- MS方法分别对碎屑状和土状铝土矿样品进行了全岩地球化学、锆石U- Pb定年、Hf同位素和锆石微量元素分析。结果显示两件样品为陆壳的、与造山/弧作用相关的花岗岩类锆石,其U- Pb年龄分布从晚泥盆世到太古宙(406~3054 Ma)均有出现,主要显示出4个年龄区间:410~630 Ma、732~1251 Ma、1405~1757 Ma和2409~2553 Ma,但高峰在732~1251 Ma,峰值年龄出现在800 Ma和1000 Ma,且锆石εHf(t)值主要分布在-15~10间。铝土矿和韩家店组、黄龙组一致的碎屑锆石年龄分布和沉积古地理环境暗示后两者是铝土矿最直接的母岩。通过对比华南板块不同地层的地质特征、锆石U- Pb年龄和Hf同位素,发现来自江南造山带西段和华夏陆块南岭- 云开地块的中新元古代长英质岩石是碎屑锆石最主要的初始物源区,而扬子西缘和北缘贡献较少。

    Abstract:

    The sedimentary- type lithium- rich bauxite deposit in the Nanchuan district of Chongqing is mainly located on the erosional surface between the Middle- Lower Silurian Hanjiadian Formation and the Liangshan Formation of Middle Permian ie. the ore bearing bed is located in the middle and lower part of the Liangshan Formation (Dazhuyuan Formation), which is an important part of the northern Guizhou and southern Chongqing bauxite metallogenic belt. As detrital zircon is abundant in bauxite, we applied a variety of analytical techniques on clastic and earthy bauxite samples, including all- rock geochemistry, zircon U- Pb dating, zircon Hf isotopes, and zircon trace elements. The results show that the two samples are mainly granite- type zircons that are related to orogenic/arc interactions. Their U- Pb age distributions appear to be from the Late Devonian to the Archean (406~3054 Ma), showing four main age ranges: 410~630 Ma, 732~1251 Ma, 1405~1757 Ma and 2409~2553 Ma. The peak age appears at 800 Ma and 1000 Ma, and the zircon ε Hf ( t ) values are mainly distributed in -15 to 10. The consistent age distribution of clastic zircon and the sedimentary paleogeographic environment of the bauxite, the Hanjiadian Formation and the Huanglong Formation indicate that the latter are the most direct parent rock of bauxite. By comparing the geological characteristics and zircon U- Pb ages and Hf isotopes from different strata in the South China Plate, we found that the Sino- Neoproterozoic perilithic rocks from the western part of the Jiangnan Orogen and the Nanling- Yunkai block of the Huaxia continental plate are the most important source area, with smaller contribution from the western and northern margins of the Yangtze.

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钟海仁,孙艳,赵芝,王成辉.2020.重庆南川铝土矿物源分析:碎屑锆石U- Pb定年、Hf同位素和锆石微量元素示踪[J].地质学报,94(5):1505-1524.
ZHONG Hairen, SUN Yan, ZHAO Zhi, WANG Chenghui.2020. Provenance of bauxite deposits in the Nanchuan district, Chongqing: evidence from U- Pb dating, Hf isotopes and trace elements in detrital zircons[J]. Acta Geologica Sinica,94(5):1505-1524.

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  • 收稿日期:2019-12-12
  • 最后修改日期:2020-03-28
  • 录用日期:2020-04-13
  • 在线发布日期: 2020-04-15
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