Lead isotope variability of fine-grained river sediments in Tibetan Plateau water catchments: Implications for geochemical provinces and crustal evolution
Lead isotope variability of fine-grained river sediments in Tibetan Plateau water catchments: Implications for geochemical provinces and crustal evolution
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DOI：
10.1016/j.lithos.2013.11.013
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发表时间：
2014-03
期刊：
影响因子：
3.5
通讯作者：
H. Tan;Jun Chen;W. Rao;Jiedong Yang;J. Ji;A. Chivas
中科院分区：
文献类型：
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作者：
H. Tan;Jun Chen;W. Rao;Jiedong Yang;J. Ji;A. Chivas
青藏高原的地壳结构记录了多期地壳经历解体、聚合和合并的动力学过程。从这三个过程可以最好地了解大陆壳的动态演变。然而，青藏高原详细的地球化学省划分和古构造亲合性或古构造演化尚不清楚。本文对青藏高原各流域细颗粒河流沉积物的酸不溶组分进行了铅同位素和微量元素的测定。本研究旨在揭示青藏高原铅同位素特征，划分不同铅同位素地球化学省，并追踪和揭示青藏高原各构造单元的构造亲缘关系。结果表明，通过弱酸化学处理，可以利用细粒河流沉积物的铅同位素特征来代表和区分地球化学省。铅同位素特征可区分不同的地球化学省和不同构造单元的古亲缘关系。受构造演化的制约，青藏高原构造单元可划分为5个铅同位素地球化学省：祁连地体;北方青藏高原地球化学省，包括东昆仑-柴达木地体、松潘-甘孜地体和东羌塘地体;北方拉萨地体; 4）拉萨地体南部; 5）喜马拉雅地体。关于祁连地体和松潘-甘孜地体的古亲缘关系的争论，细颗粒河流沉积物的Pb同位素组成表明，它们更可能是从扬子区分离出来的，而不是从华北区分离出来的。东昆仑-柴达木地体和东羌塘地体的铅同位素和微量元素特征与松潘-甘孜地体具有一定的相似性，表明它们也可能起源于扬子板块的解体。拉萨地体南部和北方的Pb同位素组成和微量元素组合不同，是由于喜马拉雅古陆壳放射性Pb同位素和低放射性Pb同位素的特提斯地幔物质的不同部分熔融和混染所致。这些因素也导致了两个不同地球化学省的演化。
The crustal structure of the Tibetan Plateau records the dynamic processes of several terranes that underwent disaggregation, aggregation, and amalgamation. The dynamic evolution of continental crusts is best understood from these three processes. However, the detailed geochemical province division of the Tibetan Plateau and the palaeo-tectonic affinity or evolution of terranes remains unclear. In this paper, the acid-insoluble fraction of fine-grained river sediments from catchments in the whole Tibetan Plateau was measured for lead isotopes and trace elements. This study aims to reveal lead isotopic characteristics, to delineate different lead isotope geochemical provinces, and to trace and uncover the tectonic affinities of various terranes in the Tibetan Plateau. Results show that by weak acid chemical treatment, the characteristics of the Pb isotopes of fine-grained river sediments can be utilized to represent and discriminate geochemical provinces. The characteristics of Pb isotopes enable the identification of different geochemical provinces and the palaeo-affinity of various tectonic units. Constrained by tectonic evolution, the Tibetan Plateau tectonic units can be divided into the following five Pb isotope geochemical provinces: 1) Qilian Terrane; 2) Northern Tibetan Plateau geochemical province, including Eastern Kunlun-Qaidam, Songpan-Ganzi and Eastern Qiangtang Terrane; 3) Northern Lhasa Terrane; 4) Southern Lhasa Terrane, and 5) Himalaya Terrane. In relation to the controversy concerning the palaeo-affinity of the Qilian and Songpan–Ganzi Terranes, the Pb isotopic compositions of fine-grained river sediments suggest that they were much more likely separated from the Yangtze Craton than from the North China Craton. The characteristics of Pb isotopes and trace elements of the Eastern Kunlun–Qaidam and Eastern Qiangtang Terrane show some similarities with the Songpan–Ganzi Terrane, which indicate that they also possibly originated from the disaggregation of the Yangtze Craton. The various partial melting and contamination of the old Himalaya continental crust from radiogenic Pb isotopes and Tethys mantle materials with low radiogenic Pb isotopes caused different Pb isotopes and trace elemental associations in the Southern and Northern Lhasa Terranes. These factors also led to the evolution of the two different geochemical provinces.