拉萨地块南木林盆地北缘中新世高锶低钇岩浆作用:锆石U-Pb年龄、Hf同位素和地球化学特征

发布时间：2018-01-26 01:49

本文关键词： 南木林盆地拉萨地块花岗斑岩高锶低钇斑岩中新世伸展背景　出处：《地质论评》2017年03期 　论文类型：期刊论文

【摘要】：拉萨地块南木林盆地北缘的林子宗群火山岩地层侵位有大量的花岗斑岩岩株和岩脉,空间分布上与南北向正断层的次级断裂相一致。本次研究对南木林盆地北缘的花岗斑岩进行了系统的元素地球化学,LA-MCICP-MS锆石U-Pb年代学和Lu-Hf同位素测试。数据结果表明:花岗斑岩具有高硅(68.31%~71.34%)、高钾(4.52%~4.96%)、高(La/Yb)N(21.59~36.81)、Sr/Y(Sr/Y=15.59~38.10)等特征,富集大离子亲石元素(LILE),亏损高场强元素(HFSE);花岗斑岩LA-MC-ICP-MS锆石U-Pb年龄为12.2±0.1Ma,ε_(Hf)(t)值为-0.6~+4.0。拉萨地块南木林盆地北缘花岗斑岩岩石学、地球化学特征显示其为新生下地壳部分熔融产物,且源区残留了石榴子石、金红石、角闪石,无斜长石残留,在岩浆上侵过程中,发生了碱性长石的分离结晶作用。花岗斑岩侵位于中新世,与区内南北向裂谷发育时代一致,成分上类似于拉萨地块南部同时期发育的高锶低钇斑岩、钾质岩,同为印度—欧亚大陆碰撞后东西向伸展背景产物。
[Abstract]:There are a large number of granitic porphyry plants and veins in the volcanic strata of the Linzizong Group in the northern margin of the South Mulin Basin in Lhasa block. The spatial distribution is consistent with the secondary faults of the normal fault in the south and north direction. The element geochemistry of the granitic porphyry in the northern margin of the southern Mulin basin has been systematically studied in this study. LA-MCICP-MS zircon U-Pb geochronology and Lu-Hf isotopic measurements. The data show that the granitic porphyry has a high silicon content of 68.31 and 71.34. High potassium 4.52 / 4.96, high La / Yb / N21.59N / 36.81 / S / S / Y / S / Y 15.59 / 38.10). The large ion lithophile element Lilei is enriched, and the high field strength element is depleted. The LA-MC-ICP-MS zircon U-Pb age of granitic porphyry is 12.2 卤0.1 Ma. The 蔚 -0.6-4.0. the petrology of granitic porphyry in the northern margin of the southern Mulin basin in Lhasa block shows that the porphyry is a partial melting product of the lower crust. And the garnet, rutile, amphibole and no plagioclase remained in the source area. During the magmatic transgression, the alkaline feldspar was separated and crystallized. The granitic porphyry transgression occurred in the Miocene. The composition is similar to that of high strontium and low yttrium porphyry and kalitic rock developed in the southern Lhasa block during the same period and is the product of east-west extension after the collision between India and Eurasia.
【作者单位】：中国地质科学院矿产资源研究所国土资源部成矿作用与资源评价重点实验室;成都理工大学地球科学学院;
【基金】：地调项目(编号:12120114068401) 公益性行业专项(编号:201511022-02)的成果~~
【分类号】：P588.1;P597.3
【正文快照】： 自从印度、欧亚板块在45~65Ma碰撞以来(莫壳板片部分熔融(Qu Xiaoming et al.,2004)、交代宣学等,2003;莫宣学,2011),碰撞后岩浆活动广泛地幔楔部分熔融(Gao Yongfei et al.,2007)等几种分布于青藏高原之上,包括钾质—超钾质火山岩、高观点。本人在南木林盆地北缘,申扎—定结

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