U-Pb zircon constraints on the tectonic evolution of southeastern Tibet, Namche Barwa area
U-Pb zircon constraints on the tectonic evolution of southeastern Tibet, Namche Barwa area
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DOI：
10.2475/ajs.304.10.889
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发表时间：
2004-12-01
影响因子：
2.9
通讯作者：
Chamberlain, CP
中科院分区：
文献类型：
--
作者：
Booth, AL;Zeitler, PK;Chamberlain, CP
喜马拉雅山脉的东部构造在地壳中表现为造山带明显的向南弯曲。地质特征走向的变化与南迦巴瓦地区地势较高、麻粒岩级变质岩出露、雅鲁藏布江180度弯相吻合。我们对西藏东南部南迦巴瓦地块及其下方地体采集的几套花岗岩进行了年代学和地球化学调查，范围从厘米级的岩脉和岩基到更大的露头级侵入体。 U-Pb SHRIMP-RG 锆石年龄确定了至少 5 个岩浆期：类似于 400 至 500 Ma、类似于 120 Ma、40 至 70 Ma、18 至 25 Ma 和 3 至 10 Ma。这些事件与样本地点的空间模式广泛相关，如下所示：从地块内部收集的锆石岩心中出现了 400 至 500 Ma 的年龄；类似于120 Ma花岗岩，与早期冈底斯岛弧深成作用有关，主要位于南迦巴瓦峰东北部；后来（40 - 70 Ma）冈底斯活动表现在南迦巴瓦以西的花岗岩中。 18至25Ma花岗岩沿甲拉佩里以西的缝合带和南迦巴瓦正北的加里断裂带区域出现，归因于加里断裂带内的剪切和早中新世冈底斯逆冲事件。异常年轻（
The eastern syntaxis of the Himalayas is expressed in the crust as a pronounced southward bend in the orogen. The change in strike of geologic features coincides with the high topography of the Namche Barwa region, the exposure of granulite-grade metamorphic rocks, and a 180-degree bend in the Yalu Tsangpo. We have conducted a geochronologic and geochemical investigation of several suites of granitoids collected from the Namche Barwa massif and subjacent terranes of southeastern Tibet, ranging from cm-scale dikes and sills to larger, outcrop-scale intrusions. U-Pb SHRIMP-RG zircon ages establish at least five magmatic episodes: similar to400 to 500 Ma, similar to120 Ma, 40 to 70 Ma, 18 to 25 Ma, and 3 to 10 Ma. These episodes broadly correlate to spatial patterns in sample localities, as follows: 400 to 500 Ma ages occur in zircon cores collected from within the massif proper; similar to120 Ma granites, related to early Gangdese arc plutonism, are primarily located northeast of Namche Barwa; later (40 - 70 Ma) Gangdese activity is expressed in granites west of Namche Barwa. 18 to 25 Ma granites occur both along the suture zone west of Gyala Peri, and directly north of Namche Barwa along the area of the jiali fault zone, and are attributed both to shearing within the jiali fault zone and to an early Miocene Gangdese Thrust event. Exceptionally young (