A record of post-collisional transition: evidence from geochronology and geochemistry of Palaeozoic volcanic rocks in the eastern Junggar, Central Asia
A record of post-collisional transition: evidence from geochronology and geochemistry of Palaeozoic volcanic rocks in the eastern Junggar, Central Asia
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DOI：
10.1080/00206814.2016.1160800
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发表时间：
2017-07
影响因子：
2.6
通讯作者：
Ting-Chuan Luo;Qun’an Liao;Ji-ping Chen;Chao-nan Hu;Fuming Wang;Shuaiqi Chen;Weiwei Wu;Jianji Ti
中科院分区：
文献类型：
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作者：
Ting-Chuan Luo;Qun’an Liao;Ji-ping Chen;Chao-nan Hu;Fuming Wang;Shuaiqi Chen;Weiwei Wu;Jianji Ti
摘要东准噶尔晚古生代火山岩记录了中亚造山带西南缘碰撞后转换的丰富线索。这些火山岩为了解岩浆和构造转换过程提供了一个更好的窗口。本文详细报道了该地区火山岩的岩石学、全岩和Sr-Nd-Pb同位素地球化学及原位锆石U-Pb定年分析。系统的地球化学和年代学研究表明，该区记录了三期岩浆活动，包括约1000年至约2000年。第407章我和你340 Ma中-高钾钙碱性系列和约320 Ma碱性岩系和拉斑玄武岩系。CA。407 Ma火山岩具有钙碱性成分，大离子亲石元素强烈富集，高场强元素亏损，Nb负异常，稀土元素轻富集的特征。CA。340 Ma火山岩具有相似的钙碱性成分和弧地球化学亲合性，但K含量较高，Th/Yb和Ba/Nb值略低于典型的岛弧或陆缘火山岩套。CA的组成。320 Ma火山岩呈双峰分布; 320 Ma玄武岩的化学成分与洋岛玄武岩（OIB）相似，但Nb、Ta略有亏损，酸性岩石具有A型花岗岩的特征。这些火山岩的化学成分表明，约。407 Ma岩浆活动与俯冲作用有关，而约407 Ma岩浆活动与俯冲作用有关。340米和。320 Ma火山岩是碰撞后岩浆作用的产物。从CA的过渡。第407章我来了320 Ma记录了板片俯冲、板片断离和板片回滚，为东准噶尔泥盆纪以来岩浆活动复杂的时空地球化学演化提供了合理的解释。
ABSTRACT Abundant clues about the post-collisional transition in the southwestern margin of the Central Asian Orogenic Belt (CAOB) have been recorded by the late Palaeozoic volcanic rocks in the eastern Junggar region. These volcanic rocks provide a better window for understanding the magmatic and tectonic transition processes. This paper reports detailed petrology, whole-rock and Sr–Nd–Pb isotope geochemistry, and in situ zircon U–Pb dating analyses of these volcanic rocks from this region. Systematic geochemical and geochronological studies show that three stages of magmatism were recorded in this area, including ca. 407 Ma and ca. 340 Ma medium-to-high-K calc-alkaline series and ca. 320 Ma alkaline and tholeiite series. The ca. 407 Ma volcanic rocks have calc-alkaline compositions, strong enrichment in large-ion lithophile elements (LILEs) and depletion in high-field strength elements (HFSEs), negative Nb anomalies, and light REE (rare earth element)-enriched patterns. The ca. 340 Ma volcanic rocks, which have similar calc-alkaline compositions and arc geochemical affinities but higher K content, have slightly lower Th/Yb and Ba/Nb values than typical island arc or continental margin volcanic suites. The compositions of the ca. 320 Ma volcanic rocks display a bimodal distribution; the ca. 320 Ma basaltic rocks are chemically similar to oceanic island basalt (OIB) but with slight depletion in Nb and Ta, wheres the acidic rocks show the features of A-type granite. The chemical compositions of these volcanic rocks indicate that the ca. 407 Ma magmatism was subduction related, while the ca. 340 Ma and ca. 320 Ma volcanic rocks were the product of post-collisional magmatism. This transition from ca. 407 Ma to ca. 320 Ma records slab subduction, slab break-off, and slab rollback and provides a plausible explanation for the complex spatial and temporal geochemical evolution of magmatism in eastern Junggar since the Devonian.