福建泰宁地区早古生代二长花岗岩年代学、地球化学特征及地质意义  

Geochronology,Geochemical Characteristics and Geological Significance of Early Paleozoic Monzogranite in Taining Area,Fujian Province

作　　者：王双 魏俊浩[1] 陈梦婷 徐崇文 高强 张声桃 胡月 WANG Shuang;WEI Junhao;CHEN Mengting;XU Chongwen;GAO Qiang;ZHANG Shengtao;HU Yue(Faculty of Earth Resources,China University of Geosciences(Wuhan),Wuhan 430074,Hubei,China;School of Geology and Mining Engineering,Xinjiang University,Urumqi 832100,Xinjiang,China)

机构地区：[1]中国地质大学(武汉)资源学院,湖北武汉430074 [2]新疆大学地质与矿业工程学院,新疆乌鲁木齐832100

出　　处：《大地构造与成矿学》2023年第4期856-877,共22页Geotectonica et Metallogenia

基　　金：国家自然科学基金项目(41772071);新疆维吾尔自治区教育厅天池博士计划项目(TCBS202001)联合资助。

摘　　要：华南早古生代武夷‒云开造山带以强烈的变质变形、区域角度不整合和发育大量花岗岩为特征。在武夷地区I型花岗岩主要分布于深大断裂等构造带附近。本文以产于武夷造山带中段石城‒崇安断裂附近的长兴二长花岗岩为研究对象,对其开展年代学、地球化学和Sr-Nd-Hf同位素分析,据此探讨岩石成因及其形成的构造背景。LA-ICP-MS锆石U-Pb年龄为451±3 Ma,表明二长花岗岩形成于晚奥陶世。岩石具有较高的SiO_(2)(71.97%~74.94%)、Al_(2)O_(3)(13.16%~14.86%)和K2O(4.03%~6.95%)含量,较低的MgO(0.27%~0.78%)、TiO_(2)(0.09%~0.26%)、CaO(0.15%~1.44%)和P2O5(0.03%~0.11%)含量,属于高钾钙碱性系列。长兴二长花岗岩具有明显的负Eu异常(δEu=0.44~0.99),富集大离子亲石元素(K、Rb)、Th、U、Pb和轻稀土元素,亏损Ba、Sr、P、Zr、Ti和重稀土元素,显示高分异I型花岗岩的特征。二长花岗岩的锆石Hf同位素具有明显的不均一性,176Hf/177Hf值介于0.282291~0.282647之间,εHf(t)值范围为–7.48~4.46,tDM2(Hf)变化于1058~1718 Ma。全岩(87Sr/86Sr)i为0.7101~0.7156,εNd(t)为–14.7~–11.7,tDM2(Nd)为1971~2171 Ma。综合分析认为武夷‒云开造山带为早古生代陆内造山带,二长花岗岩形成于后造山伸展垮塌阶段初期,为幔源基性岩浆及其上涌诱发的酸性岩浆在地壳深部混合,并经历了高程度的分离结晶作用的产物。The Early Paleozoic Wuyi-Yunkai orogen in South China is characterized by significant metamorphism and deformation,regional angular unconformity and widespread granitoids.Most of these granitoids are suggested to be S-type granites,and a few are I-type granites.Spatially,the I-type granites in the Wuyishan area mainly occur near the deep fault zones.This study focuses on the Changxing monzogranite,which is located near the Shicheng-Chongan Fault in the centre of the Wuyi orogenic belt.The LA-ICP-MS zircon U-Pb dating yield an age of 451±3 Ma,indicating that the Changxing monzogranite was formed in the Late Ordovician.The rocks are high-K calc-alkaline and display high SiO_(2)(71.97%to 74.94%),Al_(2)O_(3)(13.16%to 14.86%),K2O(4.03%to 6.95%)and P2O5(0.03%to 0.11%)contents,but with low MgO(0.27%to 0.78%),TiO_(2)(0.09%to 0.26%)and CaO(0.15%to 1.44%)contents.The Changxing granite is enriched in K,Rb,Th,U and depleted in Ba,Sr,P,Zr and Ti,with mild negative Eu anomalies(δEu=0.44–0.99),suggestive of a highly fractionated I-type granite.The granite has highly variedεHf(t)values of–7.48 to 4.46,176Hf/177Hf values of 0.282291 to 0.282647,and tDM2(Hf)values of 1058 Ma to 1718 Ma.The granite has(87Sr/86Sr)i ratios range from 0.7101 to 0.7156,theεNd(t)values vary from–14.7 to–11.7,and the tDM2(Nd)values of 1971 Ma to 2171 Ma.It can be inferred that the Changxing granite is the product of the crust-mantle interaction in a post-collision extension environment.The granitic magma was formed by mixing of the mantle-derived basic magma and acidic crustal melts,and then underwent high-degree fractional crystallization.

关 键 词：高分异I型花岗岩 陆内造山带 早古生代 华南 壳幔混合作用 后碰撞‒伸展 

分 类 号：P595[天文地球—地球化学] P597[天文地球—地质学]