| 滇东南南温河花岗岩年代学和地球化学初步研究 |
| 其他题名 | Primary research on geochronology and geochemistry of Nanwenhe granite , southeast Yunnan
|
| 徐伟
|
| 2007-05-17
|
| 学位授予单位 | 中国科学院地球化学研究所
|
| 学位授予地点 | 地球化学研究所
|
| 学位名称 | 博士
|
| 关键词 | 滇东南
南温河花岗岩
地球化学
同位素年代学
构造演化
|
| 摘要 | 南温河花岗岩分布于中-越接壤处的云南省马关县、麻栗坡县老君山地区穹隆状变形-变质岩系的内核部位，大地构造位置位于华南褶皱带西端与上扬子地块、哀牢山褶皱带和印支地块的接合部位，是研究华南大陆形成与演化及特提斯构造域时空发展的关键地区。前人对本地区花岗岩的研究，更多的集中在燕山期老君山花岗岩的研究上，而对南温河花岗岩的研究还没有引起足够的重视，还停留在初步的岩石学和地球化学阶段。
本文对滇东南老君山地区南温河花岗岩进行了U-Pb、Rb-Sr同位素年代学和主微量、Sr-Nd同位素地球化学的系统研究，取得了以下主要认识：
1、通过对南温河花岗岩 SHRIMP锆石U-Pb、TIMS锆石U-Pb年代学和全岩Rb-Sr年代学的研究，确定了南温河花岗岩主体的结晶年龄为440Ma左右，少量结晶为420Ma左右， 属于广西运动产物。在同位素年代学和岩石学研究基础上，重新对南温河花岗岩进行了岩石单元划分，归并为猛洞河单元和南加河单元两个单元。南捞片麻岩并非如1：50000麻栗坡县幅、都龙幅所认为的新元古代岩浆岩，也同属加里东期岩浆岩，应归属于猛洞河单元。
2、南温河序列花岗岩成分来源主要为上部地壳的泥质岩、粉砂岩、杂砂岩的部分熔融，可能还有少量地幔物质和下部地壳物质的加入。成因上主要属于S型花岗岩，少量属于 I型花岗岩。 形成的构造环境上，主要为同碰撞环境，少部分为造山后环境。 继承锆石年龄和Sr-Nd同位素地球化学特征显示，源区存在古元古代的古老地壳。
3、结合SHRIMP和TIMS锆石U-Pb年代学两种测年方法的差异，确定了后期的主变质年龄为 230Ma左右，提出了确定后期中-浅变质作用年龄的一种新思路。
4、通过南温河花岗岩热年代史反演，恢复了本区加里东期以来的构造历史，并初步探讨了本区加里东期的大地构造环境。 |
| 其他摘要 | The Nanwenhe granites locates in the inner core of the Laojunshan deformed-metamorphic Dome crops out in the Laojunshan area, where on the border between China and northern Vietnam, strides over the Maguan and Malipo counties, Yunnan Province, China. On the tectonic setting, this Dome locates in the west prone of South China Fold Belt, where closes to the Yangtze Block, the Ailaoshan Fold Belt and the Indochina Block. The Laojunshan area is one of the key to understand the history of the South China Continent and the space-time frame of the eastern Tethys. Most studies on the geology and the resources of this area focus on the Yanshanian Laojunshan granites, by contrast, a few studies, which mainly on the petrology and geochemistry in preliminary, on the Nanwenhe granites has been done.
Based on the geochronology and geochemistry of the Nanwenhe granites, we get some conclusions in this dissertation:
1、The majority of the Nanwenhe granites formed at ca. 440Ma, and minor at ca. 420Ma, by means of the SHRIMP/TIMS U-Pb zircon dating and whole rock Rb-Sr dating. Both ages suggest that the Nanwenhe granites should be formed in the Guangxi Movement. Baesd on the geology and geochronology, the Nanwenhe granites should be divided into the Mengdonghe and the Nanjiahe units, and the Nanlao gneiss should belong to the Mengdonghe unit rather than a Neoproterozoic granitoids described in the 1/50,000 regional geological surveys.
2、The Nanwenhe granites mainly derived from partial-melting of the mudstone, siltstone and graywacke in the upper crust, and minor might derived from the lower crust and the upper mantle. The majority of the granites belong to the S-type whereas minor I-type. The geochemistry suggested that the granites were mainly formed in the syn-COLG setting while a little in the POG setting. The U-Pb ages of inherited zircons and the two stages model Nd ages, indicated that there should be the Middle-Paleo Proterozoic rocks in the regional crust.
3、The age of ca. 230Ma of the major metamorphic event has been calculated on the difference between the SHRIMP and TIMS zircon U-Pb data. The method provides a new way to dating the moderate and low grades metamorphosed rocks.
4、Based on the geochronolgy and geology, the thermal history since Caledonian Period of the granites and its implications on the tectonic of the study area even to the South China has been discussed in this dissertation. |
| 页数 | 74
|
| 语种 | 中文
|
| 文献类型 | 学位论文
|
| 条目标识符 | http://ir.gyig.ac.cn/handle/352002/3350
|
| 专题 | 研究生_研究生_学位论文
|
推荐引用方式
GB/T 7714 |
徐伟. 滇东南南温河花岗岩年代学和地球化学初步研究[D]. 地球化学研究所. 中国科学院地球化学研究所,2007.
|
除非特别说明，本系统中所有内容都受版权保护，并保留所有权利。
修改评论