大别-苏鲁造山带超高压变质岩原岩性质:锆石氧同位素和U-Pb年龄证据

被引：60

作者：

郑永飞

龚冰

赵子福

陈福坤

机构：

[1] 中国科学技术大学地球和空间科学学院

[2] 中国科学院地质与地球物理研究所合肥

[3] 合肥

[4] 北京

来源：

科学通报 | 2003年 / 02期

关键词：

锆石; 氧同位素; U-Pb; 新元古代; 裂谷岩浆; 热液蚀变; 雪球地球;

D O I：

暂无

中图分类号：

P588.3 [变质岩];

学科分类号：

摘要：

对大别-苏鲁造山带榴辉岩和花岗片麻岩中的锆石进行了激光氧同位素分析、单颗粒U-Pb年龄测定以及阴极发光观察,其中氧同位素分析样品覆盖面积达到大约20000 km2.结果表明,大多数锆石具有大的岩浆成因核和窄的变质增生边,岩浆成因核具有新元古代年龄(700～800 Ma);氧同位素比值变化较大(-10.9‰～+8.5‰),但是大多数具有比地幔锆石低的δ18O值.由于锆石的氧同位素组成不受亚固相高温热液蚀变和麻粒岩相变质作用的影响,因此这些低δ18O榴辉岩和花岗片麻岩的原岩分别为低δ18O的基性和酸性岩浆,对应于扬子板块北缘与新元古代裂谷构造有关的双模式岩浆活动.这种大面积新元古代低δ18O岩浆活动与Rodinia超大陆裂解和全球性冰川作用(雪球地球事件)具有准同时性,因此具有一定的成因联系.早期基性岩浆沿扬子板块北缘裂谷构造带侵位,岩浆作为热源引起冰川融化并引起裂谷带内部地表水深循环和热液蚀变,导致深部地壳酸性围岩和基性岩的氧同位素比值发生显著降低.而水化岩石由于其熔点降低出现重熔,结果产生了新元古代时期的扬子板块北缘的大面积双模式低δ18O岩浆活动,然后从中结晶出低δ18O锆石.因此,大别-苏鲁造山带超高压变质岩中的大规模氧同位素负异常是从其原岩新元古代低δ18O岩浆继承过来的,其成因与Rodini

引用

页码：110 / 119

页数：10

共 59 条

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