海南岛罗葵洞斑岩钼矿床地球化学特征及成矿物质来源

为了正确理解海南岛罗葵洞钼矿床赋矿斑岩体的岩石学成因与成矿之间的关系以及成矿物质来源，对矿床中含矿斑状花岗岩进行了全岩主量、微量、Sr-Nd-Pb同位素和金属硫化物S-Pb同位素等测试分析，结果表明:（1）罗葵洞斑状花岗岩具有高SiO₂（70.94%~72.59%）、Al₂O₃（15.11%~16.26%）和低MgO（0.56%~0.68%），高Sr（421×10-6~564×10-6）、低Y（7.50×10-6~14.57×10-6）和Yb（0.76×10-6~1.30×10-6）含量，较弱的负Eu异常（平均0.75），亏损HFSE，富集LREE和LILE，较高的La/Yb（26.1~46.4）与Sr/Y（36.9~67.1）比值特征，表现出与埃达克岩相似的地球化学特征；（2）斑状花岗岩的（87Sr/86Sr）_i=0.708 38~0.708 44，（143Nd/144Nd）_i=0.512 22~0.512 23，ε_Nd（t）=-5.6~-5.5，对应的T_DM2模式年龄为1.35~1.36 Ga，表明其可能形成于底侵的增厚玄武质下地壳岩石（中元古代）的重熔；（3）全岩锆饱和温度（平均795±12℃（σ））和锆石Ti温度（平均690±21℃（σ））表明斑状花岗岩岩浆来源于在水近饱和条件下发生的部分熔融；（4）锆石Ce4+/Ce3+比值范围为174~621（平均383），表明其在形成时的岩浆-热液体系的氧逸度较高，有利于Mo等成矿元素在岩浆熔体中富集，成矿潜力较大；（5）金属硫化物δ34S（平均1.7‰）和Pb同位素特征指示成矿物质来源以下地壳为主，同时伴有少量地幔成分的参与；（6）对比年代学、矿物学、地球化学和形成环境等方面后，初步认为该矿床属于Endako型斑岩钼矿床. 

Geochemical Characteristics and Ore-Forming Materials of Luokuidong Molybdenum Ore Deposit in Hainan Island

The Luokuidong porphyry Mo deposit in Hainan Island is a large-scale low-grade deposit,controlled by volcanic apparatus. In order to understand petrogenesis of ore-forming porphyry and the sources of metallogenetic material,in this paper,it presents a systematic study of the major elements,trace elements,Sr-Nd-Pb isotopic compositions of whole rocks and S-Pb isotopic compositions of metal sulfide,with the following results.(1) The geochemical characteristics of Luokuidong porphyritic granite are similar to the adakitic rock,showing high SiO₂(70.94%-72.59%),Al₂O₃(15.11%-16.26%) and low MgO (0.56%-0.68%),high Sr (421×10-6-564×10-6) and low Y (7.50×10-6-14.57×10-6),Yb (0.76×10-6-1.30×10-6),negligible Eu anomalies (average 0.75),depletion of HFSE,enrichment of LREE and LILE,high La/Yb (26.1-46.4) and Sr/Y (36.9-67.1). (2) Porphyritic granite has(87Sr/86Sr)_i=0.708 38-0.708 44,(143Nd/144Nd)_i=0.512 22-0.512 23,ε_Nd(t)=-5.6——5.5 and T_DM2=1.35-1.36 Ga,indicating they may have derived from underplating thickened lower crust (Mesoproterozoic) remelting. (3) Temperatures from the concentration of Zr in whole-rock and Ti in zircon are 795±12℃ (σ) and 690±21℃ (σ),respectively,reflecting their magmatic hydrothermal system experienced partial melting under near-water-saturated conditions. (4) The ratio Ce4+/Ce3+ (174-621,average 383) of zircons from porphyritic granite reflect a high oxygen fugacity environment when their magmatic-hydrothermal system formed. (5) S-Pb isotopic compositions of metal sulfide suggest ore-forming materials belong to crust-mantle mixed source type dominated by deep crust source. (6) The Luokuidong porphyry Mo deposit is preliminarily considered belonging to Endako type porphyry Mo deposit after comparison in chronology,mineralogy,geochemistry and forming environment,respectively.