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川东北地区七里峡剖面须家河组泥岩地球化学特征及其地质意义
Geochemical characteristics of Xujiahe Formation mudstones in the Qilixia section of northeast Sichuan area and their geological significance
投稿时间:2019-05-12  
中文关键词:古环境  地球化学特征  须家河组  三叠系  川东北
英文关键词:paleo-sedimentation  gochemical characteristics  Xujiahe Formation  Triassic  northeast Sichuan area
基金项目:中央高校基本业务费项目(2652017458)
作者单位E-mail
赖玮 中国地质大学(北京) 地球科学与资源学院, 北京 100083  
阮壮 中国地质大学(北京) 地球科学与资源学院, 北京 100083 ruanz0103@cugb.edu.cn 
王黎栋 中国地质大学(北京) 水资源与环境学院, 北京 100083  
沈臻欢 中国地质大学(北京) 地球科学与资源学院, 北京 100083  
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中文摘要:
      泥岩中对沉积环境敏感的元素或元素比值可以定性或半定量地反映古沉积环境。研究通过川东北地区七里峡剖面须家河组12件泥岩样品的扫描电镜观察,主微量元素、X射线衍射的测试分析,开展了该区古气候、古环境及物源特征研究。研究结果表明,七里峡剖面须家河组细粒泥岩样品中的粘土矿物以伊-蒙混层矿物为主(含量62%~88%),其次是绿泥石(3%~19%)、伊利石(3%~11%)、高岭石(1%~9%),FeO/MnO值为28.08~104.23,反映七里峡地区晚三叠世总体温暖潮湿的气候条件,其中须三、五段沉积期气候较为温湿,须一、二、四段沉积期气候略干热;较低的Li、Sr、Ni、Ga丰度及Sr/Ba值(0.08~0.24)揭示了须家河组泥岩沉积时水体盐度较低;V/(V+Ni)值(0.69~0.85)和Ceanom(0.26~0.30)等指示须家河组沉积时期为缺氧的还原环境,且须一段到须五段水体的还原性逐渐减弱;研究区样品的稀土元素配分曲线与南秦岭、龙门山和米仓山-大巴山地区类似,指示了区内早期物源主要来自南秦岭地区闪长岩、花岗岩和玄武岩的混合,部分来自龙门山地区的花岗岩,晚期物质来源以米仓山-大巴山花岗岩为主。
英文摘要:
      Paleo-sedimentary environment could be recovered qualitatively or semi-quantitatively by using elements or element ratios sensitive to sedimentary environment of mudstone. In this study, major, trace and rare earth elements compositions, XRD and SEM of 12 rock samples from Xujiahe Formation were analyzed to investigate the paleoclimate, paleo-sedimentation and paleo-provenance in the Qilixia section, northeast Sichuan area. The results show that the content of clay minerals in the fine-grain samples of the Xujiahe Formation in the Qilixia section is dominated by illite-montmorillonite mixed-layer mineral (62%~88%), followed by chlorite (3%~19%), illite (3%~11%), and kaolinite (1%~9%), with FeO/MnO ratios being 28.08~104.23, reflecting the warm and humid climatic conditions of the Late Triassic in the Qilixia area, in which the climate of the 3rd and 5th members of the sedimentary period were relatively warm and humid, and the climate of the 1st, 2nd and 4th members of the sedimentary period were slightly arid and hot; lower Li, Sr, Ni and Ga abundances and Sr/Ba ratios (0.08~0.24) of the Xujiahe Formation suggest that the paleo-salinity of sedimentary water was low; V/(V+Ni) ratios (0.69~0.85) and Ceanom(0.26~0.30) indicate that there existed a reducing environment in Xujiahe sedimentary period, with the reductivity of water gradually weakened from the 1st to the 5th member of the Xujiahe Formation. The REE distribution patterns of samples in the study area are similar to those in South Qinling Mountain, Longmen Mountain and Micang-Daba Mountain areas, indicating that the early provenance in this area was derived mainly from the mixture of diorite, granite and basalt in the South Qinling Mountain, with some from the granite of Longmen Mountain, whereas the late provenance was mainly derived from the granite of Micang-Daba Mountain.
赖玮,阮壮,王黎栋,沈臻欢,2019,川东北地区七里峡剖面须家河组泥岩地球化学特征及其地质意义[J].岩石矿物学杂志,38(5):657~672.
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