牡丹江地区黑龙江杂岩锆石U-Pb年代学特征及地质意义

黑龙江杂岩主要出露在佳木斯地块西缘，沿牡丹江断裂分布，为佳木斯地块与松嫩地块拼合过程中形成的构造混杂岩.杂岩以强烈变形的长英质糜棱岩为主体，其中含有大量具洋壳性质的超基性岩、变基性熔岩（蓝片岩）及变硅质岩和大理岩等岩块或岩片.对出露于黑龙江省东部牡丹江地区的长英质糜棱岩进行了锆石LA-ICP-MS研究.获得两组²⁰⁶Pb/²³⁸U年龄数据，其加权平均年龄分别为509.4±7.1 Ma（n=9，MSWD=1.3）和269±1.9 Ma（n=22，MSWD=0.93）.其中最老2 420和2 459 Ma锆石年龄的出现，表明杂岩中有来自古元古界古老物质；509 Ma左右是佳木斯地块中麻山群的高级变质和花岗质岩浆作用年龄；约269 Ma年龄说明黑龙江杂岩变形基质形成于晚二叠世之后，可能与晚古生代古亚洲洋闭合事件相关.

ZIRCON U-Pb CHRONOLOGY OF THE HEILONGJIANG COMPLEX IN MUDANJIANG AREA: Geological Implication

The Heilongjiang complex, mainly occurred in the western margin of Jiamusi massif along Mudanjiang fault, is a tectonic melange formed during the suturing of Jiamusi massif and Songnen massif. The complex is dominated by strongly deformed felsic mylonite, which contains a large number of ultrabasic rocks, metabasic lava (blueschist), meta-silicalite and marble blocks or slices with the nature of oceanic crust. The zircon LA-ICP-MS U-Pb dating of felsic mylonites in Mudanjiang area yields two groups of ²⁰⁶Pb/²³⁸U age data, with the weighted mean ages of 509.4±7.1 Ma (n=9, MSWD=1.3) and 269±1.9 Ma (n=22, MSWD=0.93). The zircons with the oldest ages of 2 420 and 2 459 Ma indicate that the complex contains ancient Paleoproterozoic materials. The age about 509 Ma is for advanced metamorphism and granitic magmatism of Mashan Group in Jiamusi massif. The age about 269 Ma suggests the deformed matrix of Heilongjiang complex be formed after Late Permian, which may be related to the closure of Paleo-Asian Ocean in Late Paleozoic.