闽北浦城地区元古代侵入岩时代及其构造环境讨论

On the time and Tectonic Environment of Proterozoic Intrusive Rocks in Pucheng Area of Northern Fujian

在闽北建宁发现年龄为１７１４±２０Ｍａ最早一期的上坪岩体以后，近年又相继在浦城地区发现元古代的侵入岩。它是岩脉、岩瘤侵入于老变质岩中，其中超基性岩测得Ｓｍ－Ｎｄ等时线年龄为１５６６．９Ｍａ，片麻状钾长花岗岩中获得单锆石Ｐｂ－Ｐｂ年龄８６５Ｍａ，将其时代分别确定为中元古代和晚元古代。根据钐钕稳定同位素特征，超基性岩反映大陆壳岩石的演化特点或者有陆无物质严重混染，稀土分配模式与高铝玄武岩相似，表明它们形成于大陆边缘。片麻状钾长花岗岩据石英氧同位素δ１８Ｏ１１．６７‰，为改造型花岗岩，ｌｇτ－ｌｇσ图解表明形成于造山带构造环境。这一最新成果对进一步研究我省前寒武纪构造及岩浆演化具有重要意义。

After discovering the Shangping Massif of 1 714 Ma in Jianning County of Northern Fujian, the Proterozoic intrusive rocks have been found out recently in Pucheng area, which intrude into the old metamorphic rocks as the form of veins or bosses. In the Proterozoic intrusive rocks, the Sm-Ndisochronal age of the ultrobasic rock is 1 566. 9 Ma and Ph-Pb isotopic age of single zircons from thegneissoid moyite 865 Ma, which are defined as middle Proterozoic and late Proterozoic respectively. It is inferred that the ultrobasic rock in the Pucheng area takes forms in the continental margin and the gneissoid moyite forms in the environment of the orogenic belt. The above-mentioned results are of significance for further study of Precambrian structures and magmatic evolution in Fujian Province.