【摘要】 对江南隆起带中段湘东西园坑岩体和赣西九岭岩体的LA-ICPMS锆石U-Pb年代学测定和LA-MC-ICPMS锆石Hf同位素原位分析测试表明:西园坑岩体形成于(804±3)Ma,赣西九岭岩体的年龄为(813±4)Ma和(823±2)Ma,均为新元古代花岗岩。上述三个样品的εHf(t)的加权平均值分别为0.68±0.71,2.3±1.7和2.2±1.1,均为正值,且其中εHf(t)最大正值的模式年龄为1096Ma。结合其较高的全岩δ18O,较靠近零的全岩εHf(t)值等地球化学特征,并通过与江南隆起带东北段的皖南许村、歙县、休宁岩体和西南段桂北三防、本洞、田朋岩体的Hf同位素组成进行对比,我们认为,湘东-赣西新元古代花岗岩的源区物质除中元古代地壳物质以外,应有一定新生地幔物质的参与。其形成机制可能受到了碰撞造山作用后的伸展垮塌的影响。更多还原

【Abstract】 This paper presents the LA-ICP-MS zircon U-Pb dating and the zircon in-situ Hf isotopic analytical results for the Neoproterozoic granites from the eastern Hunan and western Jiangxi Provinces. The dating results show that zircons separated from the Xiyuankeng and Jiuling plutons yielded the weighted mean 206Pb/238U age of (804±3)Ma,(813±4)Ma and (823±2)Ma,respectively. They have positive zircons εHf(t) values of 0.68±0.71,2.3±1.7 and 2.2±1.1,respectively. One grain with the highest positive εHf(t) value of 7.12 gives the Hf model age of 1096Ma. Considering the geochemical signatures (e.g.,high δ18O values and εHf(t) values nearing to zero) for the Jiuling intrusion and the zircon Hf isotopic composition variation for the synchronous granites in the southern Anhui and western Guangxi Provinces,it is proposed that the Neoproterozoic granites were derived from the Mesoproterozoic crustal materials with involvement of juvenile mantle component. It is inferred that the petrogenesis of the granites are related to the collapse of post-collision.更多还原