鄂西走马地区南华纪古城期-南沱早期古气候和古氧相演化:来自细碎屑岩元素地球化学的证据
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本文为国家自然科学基金项目(编号41872238)和湖北省地质局科技项目(编号KJ2017- 11、KJ2018- 4)共同资助的成果。


Paleoclimate and paleo- oxygen evolution during the Gucheng Period- early Nantuo Period of Nanhua System in the Zouma area, West Hubei:evidence from elemental geochemistry of fine clastic rocks
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    摘要:

    新元古代后期地球经历了至少两次全球规模的冰川期,分别为Sturtian冰期和Marinoan冰期。鄂西走马地区南华系古城组与南沱组分别属于Sturtian和Marinoan冰期沉积,大塘坡组代表间冰期沉积,同时,大塘坡期是我国重要的成锰时期。本文通过对走马地区ZK702钻孔岩心古城组、大塘坡组、南沱组底部细碎屑岩样品元素地球化学的研究,计算了CIA、CIW、PIA、Al/Ca、Rb/Sr、V/Cr、U/Th等特征值,探讨了该区南华纪冰期至间冰期的古气候和古氧相演化过程,结合岩石学证据认为:古城冰期气候寒冷干燥(CIA值从底部的69. 2过渡至57. 8,均值为62. 2),大塘坡间冰期早期气候依然寒冷(CIA值介于54. 3~62. 7,均值59. 7),大塘坡中晚期气候恢复温暖湿润并趋于稳定(CIA值介于70. 2~81. 1,均值75. 8),南沱冰期气候又转向寒冷干燥(CIA值由78. 6降低至61. 9),CIW、PIA、Rb/Sr值等指标反映的古气候演化过程与CIA值反映一致,Al/Ca值的变化也反映了陆源碎屑输入量随着古气候波动;V/Cr、U/Th、Ni/Co等比值反映出研究区古海洋古城期-南沱早期总体处于氧化环境,其中大塘坡早期处于弱氧化环境,古城期、大塘坡中晚期和南沱早期处于氧化环境;研究区大塘坡锰矿形成于间冰期早期寒冷气候下的弱氧化环境,气候转暖后锰矿停止沉积,锰矿成矿与古气候和古氧相具有耦合关系。

    Abstract:

    The late Neoproterozoic witnessed at least two glacial events on a global scale, namely, the Sturtian and Marinoan. In the Zouma area of West Hubei, the Nanhua System Gucheng Formation and Nantuo Formation belong to the Sturtian and Marinoan glacial deposits respectively. The Datangpo Formation represents the interglacial deposits and is also an important Manganese- forming period. This study conducted geochemcial analysis for fine clastic rock samples of the Guchegn, Dtangbo and Nantuo formations from the ZK702 drill core in the study area, and calculated the characteristic valuses of the CIA, CIW, PIA, Al/Ca, Rb/Sr, V/Cr and U/Th, to understand the paleoclimate and paleo- oxygen facies evolution from glacial to interglacial in the Nanhua period. Petrological evidence also suggests that the climate of Gucheng glacial period was cold and dry (CIA value changed from 69. 2 at the bottom to 57. 8, at the mean value of 62. 2), and the paleotemperature of early interglacial period in the Datangpo increased and tended to stable (CIA ranging from 54. 3 to 62. 7, with a mean of 59. 7), and the climate of late Datangpo returned to warm humid and tended to be stable (CIA value ranging from 70. 2 to 81. 1, with a mean of 75. 8). The climate of the Nantuo glacial period became cold and dry again (the CIA value decreased from 78. 6 to 61. 9). The paleoclimate evolution reflected by CIW, PIA and Rb/Sr values is consistent with that of CIA values. The change of Al/Ca values also reflects that the fluctuation of terrigenous clastic was input with paleoclimate. The V/Cr, U/Th and Ni/Co ratios show that the study area during Gucheng Period to early Nantuo Period was generally in an oxidation environment. Among them, the paleo- ocean during the early stage of Datangpo period was in sub- oxidation environment, while the other periods were in the oxidation environment. The manganese in Datangpo deposited in a sub- oxidation environment in the early interglacial cold climate, and the manganese stopped deposition after the climate became warmer. The mineralization of manganese deposits was coupled with paleoclimate and paleo- oxygen facies.

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李明龙,陈林,田景春,郑德顺,许克元,方喜林,曹文胜,赵军,冉中夏.2019.鄂西走马地区南华纪古城期-南沱早期古气候和古氧相演化:来自细碎屑岩元素地球化学的证据[J].地质学报,93(9):2158-2170.
LI Minglong, CHEN Lin, TIAN Jingchun, ZHENG Deshu, XU Keyuan, FANG Xilin, CAO Wensheng, ZHAO Jun, RAN Zhongxi.2019. Paleoclimate and paleo- oxygen evolution during the Gucheng Period- early Nantuo Period of Nanhua System in the Zouma area, West Hubei:evidence from elemental geochemistry of fine clastic rocks[J]. Acta Geologica Sinica,93(9):2158-2170.

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  • 收稿日期:2018-10-07
  • 最后修改日期:2019-01-23
  • 录用日期:2019-04-12
  • 在线发布日期: 2019-04-12
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