摘要
太阳沟钼矿床位于冀东地区,矿区内出露的岩性主要为花岗斑岩和黑云母二长花岗岩,矿体主要赋存于花岗斑岩及其围岩接触带内,多呈透镜状、脉状产出。本文通过锆石U-Pb定年、全岩地球化学分析、辉钼矿Re-Os同位素测年及金属矿物S、Pb同位素分析,对太阳沟钼矿床的成岩、成矿时代准确厘定,并对矿床成因及成矿过程进行探讨。锆石U-Pb定年结果显示,花岗斑岩与黑云母二长花岗岩样品的^206Pb/^238U加权平均年龄分别为154.8±1.5Ma、156.5±1.2Ma。辉钼矿的Re-Os同位素测年获得155.79±0.93Ma的模式年龄加权平均值,与锆石U-Pb年龄在误差范围内一致,表明其为晚侏罗世构造-岩浆活动产物。全岩地球化学特征表现为高硅、富碱,属准铝质、高钾钙碱性系列;相对富集轻稀土元素和Rb、Sr等大离子亲石元素,亏损重稀土元素和Nb、Ta等高场强元素,属高分异I型花岗岩。黄铁矿S、Pb同位素分析结果表明,S同位素组成分布比较集中,δ^34S(黄铁矿)值均为正值(介于1.3‰~1.8‰之间,平均值为1.53‰);Pb同位素组成较为均一(^206Pb/^204Pb值范围为16.76~17.44,^207Pb/^204Pb值范围为15.28~15.43,^208Pb/^204Pb值范围为36.64~37.46),均显示成矿物质主要来自受地幔混染的下地壳物质熔融。综合岩石学、年代学、地球化学及S、Pb同位素特征,本文认为:太阳沟钼矿床属于斑岩型钼矿床,是晚侏罗世古太平洋板块俯冲产生的壳幔相互作用引发下地壳物质部分重熔,富集大量的金属元素(Mo),最终上升侵位、沉淀成矿。
The Taiyanggou molybdenum deposit is located in the eastern Hebei Province.Intrusions exposed in this deposit are granite porphyry and biotite monzogranite.The ore bodies mainly occur as lenticles and veins in granite porphyry and at the contact zone between granite and wall rocks.This study reports zircon U-Pb dating,whole rock geochemistry,the molybdenite Re-Os isotopic age and S,Pb isotopic analyses,which are helpful in determining the diagenetic and metallogenic epoch,and in discussing the genesis and metallogenic process of the Taiyanggou molybdenum deposit.The weighted mean ^206Pb/^208U ages of the granite porphyry and biotite monzogranite are 154.8±1.5 Ma and 156.5±1.2 Ma,respectively.Re-Os model age weighted average of molybdenite is 155.79±0.93 Ma,obtained by Re-Os isotope dating,lying within the margin of error of zircon U-Pb ages,indicating that they are the product of the late Jurassic tectonic-magmatic activity.Geochemical characteristics show that the granites have high silicon,high alkali,and belong to high-K calc-alkaline series and highly differentiated type I granite,with enrichment of large ion lithophile elements(LREE,Rb,Sr,Ba)and depletion of high field strength elements(HREE,Nb,Ta,Ti).According to the analysis of S and Pb isotopes,the composition distribution of S isotope is relatively concentrated and theδ^34Spyrite values are all positive(1.3‰~1.8‰,average of 1.53‰).The composition of Pb isotope is uniform(^206Pb/^204Pb values of 16.76~17.44,^207Pb/^204Pb values of 15.28~15.43,^208Pb/^204Pb values of 36.64~37.46),indicating that the metallogenic materials were mainly derived from the melting of the lower crust materials and mixed with the mantle.Combined with the characteristics of petrology,chronology,geochemistry and S,Pb isotopes,it is suggested that the Taiyanggou molybdenum deposit belongs to porphyry molybdenum deposit.The crust-mantle interaction caused by the subduction of the late Jurassic Pacific plate induced partial remelting of the lower crust,so as to enrich large numbers of Mo elements,and finally emplacement and sediment formed ore deposit.
作者
徐国新
李玉静
孙金龙
和越
赵迪
刘晓波
王丹
XU Guoxin;LI Yujing;SUN Jinlong;HE Yue;ZHAO Di;LIU Xiaobo;WANG Dan(Eighth Geological Brigade of Hebei Bureau of Geology and Mineral Resources Exploration,Qinhuangdao,Hebei,066001;Hebei Geological and Mineral Research Center,Shijiazhuang,050051)
出处
《地质学报》
EI
CAS
CSCD
北大核心
2020年第11期3343-3360,共18页
Acta Geologica Sinica
基金
河北省地质矿产局科研基金项目(编号454-0601-YBN-G9A6)资助的成果。
