东北牡丹江地区“黑龙江群”中斜长角闪岩与花岗岩的锆石SHRIMP U-Pb定年及其地质学意义  

Zircon SHRIMP U-Pb dating of the amphibolite from "Heilongjiang Group" and the granite in Mudanjiang area,NE China,and its geological significance.

作　　者：颉颃强[1,2] 张福勤[2] 苗来成[2] 陈福坤[2] 刘敦一[1] 

机构地区：[1]中国地质科学院北京SHRIMP中心,北京100037 [2]中国科学院地质与地球物理研究所,北京100029

出　　处：《岩石学报》2008年第6期1237-1250,共14页Acta Petrologica Sinica

基　　金：国家自然科学基金(批准号:40234045,40473030);中国科学院知识创新工程(编号:KZCX2-104)资助

摘　　要：佳木斯地块南缘牡丹江地区的岩石学和地球化学研究表明,"黑龙江群"中存在洋壳残片,为形成于古大陆边缘环境的一套造山建造。牡丹江地区东北部的"麻山群"为佳木斯地块南缘的陆壳基底;其南侧的"黑龙江群"属造山建造,包括阿尔卑斯型超基性岩和具有 MORB 特征的斜长角闪片岩等。对"黑龙江群"中的斜长角闪片岩以及其南边具有同碰撞特征的钾长花岗岩进行了锆石 SHRIMP U-Pb 定年。结果表明:斜长角闪片岩具有777±18Ma 的结晶年龄,并受到437±7Ma 的变质作用的影响;同碰撞的钾长花岗岩形成年龄为461±6Ma。据此指出佳木斯地块南缘的黑龙江群中存在新元古代的洋壳残片并推断牡丹江地区存在早古生代的碰撞事件。Lithology and geochemistry of rocks in Mudanjiang area indicate that the so-called ＂ Heilongjiang Group＂ contains remnants of oceanic crust,representing formations developed in an ancient active continental margin setting. The Mashan Group in this area is the basement of the Jiamusi Massif, and the ＂ Heilongjiang Group＂ represents the orogenic sequence, including Alpine-type lherzolite and amphibolite schist that has a geochemical affinity of MORB. SHRIMP zircon U-Pb dating shows that the amphibolite schist yielded a magmatic age of 777 ± 18 Ma, which was reworked by metamorphism at 437 ± 7 Ma; a syn-collsional granite emplaced to the south of ＂Heilongjiang＂ Group at 461 ± 6 Ma. We propose that the ＂ Heilongjiang＂ Group indicates a paleo-collisional zone and the collisional timing of the Mudanjiang collisional zone is about Ordovician-Early Silurian according to the Ca. 440Ma extensive metamorphism and the occurrence of the syn-collisional granite magmatism.

关 键 词：黑龙江群 洋壳残片 早古生代 佳木斯地块 锆石SHRIMP U—Pb定年 牡丹江 

分 类 号：P597.3[天文地球—地球化学] P588.125[天文地球—地质学]