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西藏改则盆地渐新世-中中新世沉积物中矿物组合特征及其对气候的指示意义

ISSN号：1000-6524
期刊名称：《岩石矿物学杂志》
时间：0
分类：P532[天文地球—古生物学与地层学;天文地球—地质学]
作者机构：[1]中国地质大学地球科学学院,湖北武汉430074, [2]中国地质大学生物地质与环境地质国家重点实验室,湖北武汉430074, [3]中国地质大学地质调查研究院,湖北武汉430074, [4]湖北民族学院生物科学与技术学院,湖北恩施445000
相关基金：中国地质调查局项目（1212011121261）; 国家自然科学基金项目（40921062）; 大学生自主创新资助计划（1410491A04）; 生物地质与环境地质国家重点实验室自主研究课题（GBL11307）

作者：陈江军[1], 洪汉烈[1,2], 刘钊[1], 宋鄂平[2,3,4], 王朝文[1,2], 姜高磊[1,3], 殷科[1,2], 张克信[1,2,3]

关键词：青藏高原, 改则盆地, 康托组, 常见矿物, 古气候, Tibetan Plateau, Gerze Basin, Kangtuo Formation, mineral assemblage, paleoclimate

中文摘要：

为了揭示西藏改则地区渐新世-中中新世古气候环境演化,结合改则盆地的沉积环境和沉积相,并利用X射线粉晶衍射对改则盆地的样品进行了全岩分析。结果表明,沉积物中主要矿物组成为石英、长石、方解石和少量白云石等,通过沉积物中矿物含量变化和石英/长石的比值显示青藏高原改则盆地康托组在气候总体为干冷的大背景下经历了4个阶段：Ⅰ（早渐新世）：石英含量最高,碳酸盐矿物次之,长石含量最少,白云石在该阶段出现频繁,且含量变化明显,指示气候以季节性干旱为主;Ⅱ（晚渐新世）：石英含量最高,但相比上一阶段有所下降,碳酸盐矿物和长石含量增加,指示气候进一步趋向干冷化;Ⅲ（早中新世）：石英含量最高,但相比之前两个阶段进一步减少,长石含量进一步增加,碳酸盐总体呈现增加趋势,特别是白云石,相比之前两个阶段含量增加明显以及下降的石英/长石比值,指示气候变得更为干冷;Ⅳ（中中新世）：石英含量相对上一阶段有所增加,长石和碳酸盐矿物含量降低,石英/长石比值也有所增长,但相比Ⅰ和Ⅱ阶段仍然较小,指示该阶段气候虽有所回升,但依旧处于干冷环境下。对比青藏高原隆升和全球气候变化,可知改则盆地气候阶段性变化可能是高原隆升和全球气候变化共同影响的结果。

英文摘要：

In order to reveal the paleoclimate evolution of the Oligocene-Miocene sediments in the Gerze Basin, Tibet, the authors used X-Ray diffraction（ XRD） to analyze the Mineral assemblage characteristics in combination with the sedimentary environments and sedimentary facies of Gerze Basin. The results show that the main minerals in the sediments are quartz, feldspar and calcite, with small amounts of dolomite, and their relative content varies along the section. Variations of relative values and ratios of quartz / feldspar suggest that the Gerze Basin has experienced four-stage paleoclimatic evolution： Stage Ⅰ（ early Oligocene）, characterized by high quartz and carbonate mineral content and low feldspar content; dolomite occurred frequently at this stage, and the content changed significantly, indicative of a dominant seasonal arid climate; Stage Ⅱ（ late Oligocene）, characterized by high quartz content, which, however somewhat decreased, indicating a colder and drier climate; Stage Ⅲ（ early Miocene）, characterized by high quartz content; nevertheless, compared with features of the previous two stages,the quartz content further decreased, the content of feldspar further increased, and carbonate tended to become an overall increase. Compared with the previous two stages, dolomite increased significantly whereas quartz / feldspar ratios decreased, indicating that the climate became colder and drier; Stage Ⅳ（ mid- Miocene）, during which quartz content relatively increased, feldspar and carbonate minerals content decreased, quartz / feldspar ratios also increased; nevertheless, compared with Stage Ⅰ and Ⅱ, the quartz / feldspar ratios remained small, indicating that the climate was somewhat recovered, but still in a cold and dry environment. Compared with the uplift of the Tibetan Plateau and the global climate change, the authors hold that that climatic periodic changes during Oligocene-Miocene in the Gerze Basin might have been caused by plateau uplift and the global climate change.

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