浙西南淡竹花岗闪长岩中锆石的成因研究及其地质意义
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本文为国家自然科学基金资助项目(批准号: 40572038)的成果。


Study on Petrogenesis of Zircons from the Danzhu Granodiorite and Its Geological Implications
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    摘要:

    本文对浙西南地区淡竹花岗闪长岩中的锆石群进行了形态学、地球化学和年代学的系统研究。研究结果表明, 该花岗闪长岩中存在两种不同类型的锆石: 岩浆锆石和变质锆石。前者为自形—半自形的长柱状晶体, 无色透明, 富含岩浆和矿物包裹体, 其背散射电子图像 (BSE图像) 显示出均匀的内部构造 (少数具有韵律环带构造), 其晶型指数落在钙碱性系列花岗闪长岩的范围内; 后者大多数以增生边的形式围绕岩浆锆石生长, 极少量呈他形的粒状晶体, 呈黄褐色—半透明, 其BSE图像亦呈现均匀的内部构造。这两类锆石在化学成分上有较大的差异, 表现为岩浆锆石比变质锆石明显地富U、Th、Y等阳离子置换元素。锆石LAICPMS UPb定年分析结果表明, 岩浆锆石和变质锆石分别形成于1875±33 Ma和209±12 Ma两个不同的时代, 为浙闽运动和印支运动在浙西南地区的表现提供了有力的客观证据。

    Abstract:

    This paper presents a systematic study on morphology, geochemistry and geochronology of a zircon population from the Danzhu granodiorite located in the southwest region of the Zhejiang province. The analysis results show that there are two types of zircons from the Danzhu granodiorite: magmatic zircon and metamorphic zircon. The former is characterized by euhedral—subhedral and longprismatic form, incolorness, transparence, presence of magmatic and mineral inclusions, homogeneous internal structure (occasionally with oscillatory zoning) on the section of grains revealed by backscattered electron (BSE) imaging, and analogue pattern of typological indices of zircon for those from the calcoalkaline granodiorite; the latter is characterized mainly by its occurrence as overgrowth on magmatic zircon, but it also occurs very occasionally as anhedral grains, which is yellowbrown, semitransparent, and homogeneous on the BSE imaging . These two types of zircon differ also in trace element composition, i.e., the magmatic zircon is significantly richer in the substituent elements like as U, Th and Y than the metamorphic zircon. The zircon UPb dating using LAICPMS shows that the magmatic zircon and metamorphic zircon were formed in two different periods: at 1875±33 Ma and at 209±12 Ma respectively, demonstrating the objective response for the ZheMin (Zhejiang—Fujian) movement and the Indosinian movement in the southwest region of the Zhejiang province.

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汪相,陈洁,罗丹.2008.浙西南淡竹花岗闪长岩中锆石的成因研究及其地质意义[J].地质论评,54(3):387-398,[DOI].
.2008. Study on Petrogenesis of Zircons from the Danzhu Granodiorite and Its Geological Implications[J]. Geological Review,54(3):387-398.

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  • 收稿日期:2007-12-17
  • 最后修改日期:2008-03-09
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