福建武夷山坪地钼矿辉钼矿铼-锇同位素定年及其地质意义  

Re-Os Isotopic Dating of Molybdenite of Pingdi Molybdenum Deposits in Wuyishan,Fujian Province and Its Geological Significance

作　　者：王翠芝[1,2] 李超[3] 

机构地区：[1]福州大学紫金矿业学院,福建福州350108 [2]福建省矿产资源重点实验室,福建福州350108 [3]国家地质实验测试中心,北京100037

出　　处：《岩矿测试》2012年第4期745-752,共8页Rock and Mineral Analysis

基　　金：福建省自然基金资助项目"辉钼矿中伴生铼资源的矿物学约束"(2010J01257)

摘　　要：福建武夷山坪地钼矿为中高温热液型钼矿,产于晚侏罗世钾长花岗岩岩体"层节理"及岩体与下元古界大金山组接触带的南北向断裂中。矿石自然类型主要为硅化岩型(石英脉型)、黄铁绢英岩型、花岗岩型、蚀变构造岩型。矿石构造主要有条带状、浸染状、角砾状、细脉状等构造类型。矿石结构以中粗-中细粒鳞片结构为主,局部呈现厚板状、带状(常常弯曲)。辉钼矿是唯一的矿石矿物。本研究采集坪地钼矿不同矿体、不同产状、不同标高的辉钼矿进行Re-Os同位素测年,得到等时线年龄为(102.9±1.8)Ma,MSWD=2.1,Re-Os模式年龄为(103.70±1.7)Ma～(111.6±1.6)Ma,加权平均值为(107.4±3.3)Ma,MSWD=16。MSWD均较大,说明坪地辉钼矿的成矿具有多阶段性,钾长花岗岩中细脉状、岩体"层节理"中粗脉状和断裂角砾岩带中团块状三种类型的辉钼矿分别是在(111.20±1.7)Ma～(111.60±1.6)Ma、(105.60±1.6)Ma～(107.40±1.6)Ma和(103.70±1.7)Ma三个不同的成矿阶段形成的,成矿时代属早白垩世晚期。这一同位素年龄资料为福建东南沿海浦城—宁德北西向中生代构造-岩浆带中同类矿床的形成演化与指导区域找矿提供了新的地球化学依据。Pingdi molybdenum deposit was attributed to medium-high hydrotherm type deposits, occulting in layer- joints of K-feldspar granite of Chenwulou unite of Late Jurassic and the north-south faults developed within Chenwulou maginatic body and the contact between Chenwulou magmatic body and lower Proterozoic Dajinshan formation. The ore mineralizations are of silified alteration type （ quartz vein type）, pyrite sericite quartz rock type, granite type and structural breccia type. Ore structures are of veinlet, disseminated, breccia, small vein. The ores mainly have medium and coarse-medium fine grain platy texture, and minor molybdenites are thick tabular and bent banding. Molybdenite is the only ore mineral in this molybdenum deposit. We collected molybdenites with different occurrences and elevations from different ore bodies of Pingdi molybnum deposits for Re-Os isotopic dating. The isochron age of （ 102.9 ± 1.8） Ma（ MSWD = 2.1 ）, and the model age of （ 107.4± 3.3 ） Ma （ MSWD = 16） were obtained. This results indicated the multi-stages mineralization with three types of molybdenite such as fine veins in rock of K-feldspar granite, thick veins in ＂ bedding joint＂ of K-feldspar granite and in breccia silicified rocks controlled by fractures, which were formed in different metallogenic phases, （ 111.20 ± 1.7 ） Ma - （ 111.60± 1.6） Ma, （ 105.60 ± 1.6） Ma - （ 107.40 ± 1.6） Ma and （ 103.70± 1.7 ） Ma, the mineralization periods during late stage of early cretaceous. This isotopic data provided the new geochemical evidences for Mesozoic tectonic magma evolution and guided regional ore-exploration of Pucheng-Ningde NW tectonic belt of Southeast coast of Fujian Province.

关 键 词：坪地钼矿 中高温热液矿床 辉钼矿 铼-锇同位素定年 

分 类 号：P579.3[天文地球—矿物学] P578.291[天文地球—地质学]