| 西藏则学地区古特提斯残留洋盆沉积充填及源区构造背景 |
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| 引用本文： | 周江羽,魏启荣,王健,许欢,赵闪,吉雪峰,欧波,王旭东,陈泰一.西藏则学地区古特提斯残留洋盆沉积充填及源区构造背景[J].地球科学,2018,43(6):2116-2132. |
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| 作者姓名： | 周江羽 魏启荣 王健 许欢 赵闪 吉雪峰 欧波 王旭东 陈泰一 |
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| 作者单位： | 1.中国地质大学构造与油气资源教育部重点实验室, 湖北武汉 430074 |
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| 基金项目： | 国家自然科学基金项目41572109国家自然科学基金项目41372112教育部"本科教学质量工程"专项基金项目324-G1320311635中国地质调查局1: 5万区域地质调查项目DD20160015 |
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| 摘 要： | 古特提斯残留洋盆沉积学和构造背景研究对于揭示青藏高原形成演化及其成矿规律具有重要意义.综合野外实测剖面、典型露头、岩石薄片、生物地层学和沉积地球化学等资料，开展了西藏则学地区晚古生代古特提斯残留洋盆的深水盆地地层学、沉积学、沉积演化和物源区构造背景研究.研究结果表明，研究区发育的晚古生代地层以含砾粉砂岩和泥岩、细砂岩为主，砂体以席状和透镜状为主，沉积构造丰富，晚古生代饱粉组合特征明显.残留洋盆经历了陆坡-深水盆地-陆架三角洲-滨浅海盆地-滨岸三角洲-海湾盆地的沉积充填演化历程.主量元素组成和比值具有较低的Fe2O3+MgO（5.1%~10.0%）、TiO2（0.44%~0.84%）、Al2O3/SiO2（0.12~0.26），以及较高的K2O/Na2O.微量和稀土元素组成和比值具有较高的∑REE、LREE明显富集、较高的La/Yb、（Gd/Yb）N、（La/Yb）N比值、弱的Eu负异常特征.碎屑岩主量、微量和稀土元素组成均指示物源区具有活动大陆边缘和大陆岛弧性质，研究区晚古生代处于伸展背景下的陆缘裂陷环境，构造-岩浆活动和隆升作用较为强烈，且具有较为稳定的继承性演化特征.盆地沉积充填和演化记录了海平面逐渐下降、古特提斯残留洋盆逐渐封闭的过程.
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| 关 键 词： | 沉积演化 地球化学 深水盆地 古特提斯 石油地质 西藏 构造 |
| 收稿时间： | 2018-02-01 |
Depositional Filling and Tectonic Settings of Provenance of Paleotethys Remnant Oceanic Basin in Zexue District,Tibet, China |
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| Abstract: | The study of the sedimentology and tectonic settings of the Paleotethys remnant oceanic basins is of great significance to reveal the formation, evolution, and its regularity of ore formation of the Tibetan plateau. The paleotethys remnant oceanic basin in Zexue district is located in the Lhasa block in south Gangdese zone. Based on the data such as field measured profiles, typical outcrops, rock sections, biostratigraphy and depo-geochemistry, we conducted the study on deep-water basin stratigraphy, sedimentology, sedimentary evolution and provenance tectonic settings of the Late Paleozoic paleotethys remnant oceanic basin. Current research indicates that the Late Paleozoic strata developed in the study area are mainly composed of pebbled fine clastic rocks and sandstone, which include pebbled-siltstone, mudstone and sandstone. The sand body is dominated by sheetlike and lenticular form, rich sedimentary structure, and the obvious Late Paleozoic sporo-pollen combination. The remnant oceanic basin experienced the evolutionary phases of sedimentary filling, which from continental slope-, deepwater basin-, continental shelf delta-, littoral-shallow basin-, coastal delta, to bay basin. The clastic sediment geochemical composition and their ratios of the main elements have characteristic of the lower Fe2O3+MgO (5.1%-10.0%), TiO2 (0.44%-0.84%), Al2O3/SiO2 (0.12-0.26), and higher K2O/Na2O. The results of the composition of trace and rare elements show higher ∑REE, LREE, La/Yb, (Gd/Yb)N, (La/Yb)N ratio, and weak Eu negative anomaly. It suggests that the provenance area has the characteristics of active continental margin and the continental island arc. It is concluded that the tectonic-sedimentary background of the Late Paleozoic in study area was in the continental margin rifting in extension background, intensive tectonic-magmatic activities and uplift, and the characteristic of more stable inheritance evolution. Sedimentary filling and evolution of the basin recorded the gradual regression process and the closure of the remnant oceanic basins in the Paleotethys. |
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