论文部分内容阅读
应用LA-ICP-MS U-Pb同位素原位微区定年方法及Hf同位素和微量元素分析方法,对闽西北天井坪地区混合岩中花岗闪长质新成体的锆石进行了系统研究.这些锆石具环带结构,Th/U比值较高(多数大于0.1),稀土元素配分型式左倾(富集HREE),具明显正Ce异常和负Eu异常,类似于岩浆锆石和深熔作用成因锆石的特征.锆石206Pb/238U加权平均年龄为(446.8±2.2)Ma(95% conf.,MSWD=0.88),为加里东期再造的产物.锆石的Hf(t)值变化范围为13.3～9.7,显示物源具壳源性质;其二阶段Hf模式年龄为1.7～1.9Ga,指示混合岩的原岩形成于古元古代.其寄主岩混合岩新成体具过铝质钙碱性花岗岩的特征,稀土元素配分型式和微量元素蛛网图显示它们具有与大陆上地壳岩石相似的特性.结合前人的研究,判断天井坪地区华夏地块基底物质形成于古元古代,在加里东期经历了强烈再造和深熔作用.该区古元古代变质基底加里东期再造的认识,为深入研究华夏地块加里东时期的构造演化及其与扬子地块的相互作用提供了新的依据.
The zircon zircons of granodiorite from the mixed rocks in the Tianjingping area, northwest of Fujian Province, were systematically studied using the LA-ICP-MS U-Pb isotopic microcalorimetry and Hf isotopic and trace element analysis Zircons have a zonal structure with a high Th / U ratio (mostly greater than 0.1). The REE patterns are leftward (enriched in HREE) with obvious positive Ce anomalies and negative Eu anomalies, similar to magmatic zircons and zircons The zircons have a weighted average age of 206Pb / 238U of (446.8 ± 2.2) Ma (95% conf., MSWD = 0.88), which is the product of the Caledonian reconstruction. The Hf (t) ~ 9.7, indicating that the provenance is of crustal origin. The second-stage Hf model ages range from 1.7 to 1.9Ga, indicating that the original rocks of the mixed rocks were formed in the Paleoproterozoic. The host rock mixed rocks are composed of peraluminous calc-alkaline granites , The REE patterns and the trace element cobwebs show that they have the same characteristics as the continental crustal rocks.According to previous studies, it is concluded that the basement material of the Huaxia block in the Tianjingping area was formed in the Paleoproterozoic. A strong re-creation and deep melting of the ancient Paleozoic basement area plus Caledonian understanding of recycling, for in-depth study of the tectonic evolution of the Chinese land Caledonian period and its interaction with the Yangtze block provides a new basis.