| 西藏南部侏罗纪—古近纪砂岩重矿物分析：探讨岩浆弧与大陆地块物源差异性 |
| |
| 引用本文： | 傅焓埔,胡修棉,梁文栋,EDUARDO Garzanti.西藏南部侏罗纪—古近纪砂岩重矿物分析：探讨岩浆弧与大陆地块物源差异性[J].高校地质学报,2020,26(5):530-539. |
| |
| 作者姓名： | 傅焓埔 胡修棉 梁文栋 EDUARDO Garzanti |
| |
| 作者单位： | 1. 南京大学 地球科学与工程学院，南京 210023；
2. Department of Earth and Environmental Sciences, University of Milano-Bicocca, Milano 20126, Italy |
| |
| 摘 要： | 物源分析是古地理重建与盆地分析的关键，典型的物源区包括岩浆弧、大陆地块、再旋回造山带等。重矿物种类多样，蕴含丰富的母岩信息，是物源分析的重要对象。现代砂的研究表明，不同大地构造背景下形成的沉积物具有不同的重矿物组合。遗憾的是，由于古代沉积的重矿物组合在成岩过程中会被改造，现代砂的重矿物组合与物源区的耦合规律并不能直接应用于古代砂岩。科学界尚不清楚岩浆弧与大陆地块来源的古代砂岩的重矿物特征。西藏日喀则弧前盆地与特提斯喜马拉雅侏罗纪—古近纪砂岩物源明确，要么来自亚洲大陆的冈底斯弧，要么来自印度大陆地块，是探讨岩浆弧与大陆地块来源的古代砂岩重矿物特征的绝佳场所。16件砂岩重矿物定量分析结果表明，两个物源区来源的砂岩重矿物组合均被成岩作用严重改造，辉石、角闪石等不稳定矿物消失，绿帘石等自生矿物出现；冈底斯弧来源的砂岩以出现大量绿帘石或磷灰石为特征，ZTR指数小于40；印度大陆地块来源的砂岩以出现大量锆石、电气石和金红石为特征，ZTR指数大于75。这一结果指示岩浆弧与大陆地块来源的砂岩的重矿物组合具有明显差异性，可以用来探讨物源的大地构造背景。
|
| 关 键 词： | 重矿物 物源分析 成岩作用 岩浆弧 大陆地块 西藏 特提斯喜马拉雅 日喀则弧前盆地 |
Heavy Mineral Assemblages of Jurassic-Paleogene Sandstones in Southern Tibet: Implications for Provenance Interpretations of Magmatic Arc and Continental Block |
| |
| Institution: | 1. School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China;
2. Department of Earth and Environmental Sciences, University of Milano-Bicocca, Milano 20126, Italy |
| |
| Abstract: | Provenance analysis is the key of paleogeographic reconstruction and basin analysis, whose typical end-members include “magmatic arc provenance”, “continental block probvenance”, and “recycled orogen provenance”. Kinds of heavy minerals contain a wealth of parent rock information, which are widely used for provenance analysis. Modern sand researches have shown there is a link between detrital heavy mineral assemblages and their geodynamic backgrounds. Unfortunately, this law cannot be directly applied to ancient sandstone because of the diagenesis. We know little about the heavy mineral assemblages of sandstones sourced from magmatic arc and continental block. The Jurassic-Paleogene Xigaze forearc basin and Tethys Himalayan sandstones in Tibet are either from Gangdese arc of the Asian continent or from Indian continental block, which is an excellent lab to study the heavy mineral assemblages of ancient sandstones derived from magmatic arc and continental block. The quantitative analyses result of 16 sandstones shows that: 1) heavy minerals are seriously modified by diagenesis, unstable minerals (e.g. amphibole, pyroxene) are disappeared while authigenic growth of new minerals such as epidote is common; 2) sandstones derived from magmatic arc are mainly composed of epidote or apatite, with ZTR<40; while sandstones derived from continental block are mainly composed of zircon, tourmaline and rutile, with ZTR>75. The sandstones sourced from magmatic arc and continental block yield distinctive heavy mineral assemblages, which make sense for provenance interpretation. |
| |
| Keywords: | heavy mineral provenance analysis diagenesis magmatic arc continental block Tibet Tethys Himalaya Xigaze forearc basin |
|
| 点击此处可从《高校地质学报》浏览原始摘要信息 |
| 点击此处可从《高校地质学报》下载免费的PDF全文 |
|
