摘要
通过对玮埔岩体两个代表性样品进行锆石的LA-ICP-MSU-Pb测年获得的206Pb/238U加权平均年龄分别为(429.9±3.0)Ma、(446.3±4.0)Ma,证明该岩体确实不是最早认为的印支期花岗岩,而是加里东期岩体。同时对宁化岩体一个样品的锆石LA-ICP-MSU-Pb测年结果得到206Pb/238U加权平均年龄为(448.2±2.5)Ma,同样属于加里东期岩体。进一步对闽西南清流地区玮埔和宁化岩体的锆石Lu-Hf同位素组成分析表明,εHf(t)值主要集中在-0.8～-10.4之间,且Hf二阶段模式年龄(TDM2)集中在1.72～2.34Ga之间,表明其岩浆源区来自华夏地块元古代地壳物质。并结合其他己发表的相关年代学和地球化学资料,可以推断包括玮埔和宁化岩体在内的华南内陆地区加里东期花岗岩很可能是元古宙基底深熔而成的产物;其形成与陆内地壳物质叠置加厚所引起的再造作用关系紧密。
The LA-ICPMS zircon U-Pb geochronology and Hf isotopic compositions of two Caledonian granitic plutons,the Weibu and Ninghua granites,from the Qingliu area,southwest Fujian,are reported in this paper.The LA-ICP-MS zircon U-Pb dating for two representatively samples from the Weipu granite yielded the weighted mean 206Pb/238U ages of（429.9±3.0）Ma and（446.3±4.0）Ma,respectively.This suggests that the Weipu granite was crystallized at 429~446Ma Caledonian rather than Indosinian period as previously believed.Our dating results show that the Ninghua pluton gave a weighted mean 206Pb/238U ages of（448.2±2.5）Ma,suggestive of the Caledonian intrusion.Zircon Hf isotopic compositions for the Weipu and Ninghua granitic plutons exhibit the εHf values of-0.8^-10.4 and two-stage model ages（TDM2） ranging from 1.72Ga to 2.34Ga,indicative of the derivation from Proterozoic continental basement of the SCB.In conjunction with other published geochronological and geological data,it is proposed that the Caledonian granites in the hinterland of the South China Block,including Weibu and Ninghua plutons,are the derivation of the Cathaysian Proterozoic basement in response to the Caledonian intracontinental tectonic setting.It is also inferred that a significant reworking has been undergone for the South China basement during the Caledonian period.
出处
《大地构造与成矿学》
EI
CAS
CSCD
北大核心
2010年第3期408-418,共11页
Geotectonica et Metallogenia
基金
中国科学院知识项目(KZCX2-YW-128
KZCX1-YW-15-1)
973项目(2007CB411403)
国家自然科学基金(40825009
40830319和40772129)的联合资助
