河北省四拨子-六拨子钼铜矿区侵入岩 LA-ICP-MS锆石U-Pb定年及成矿意义

河北省青龙满族自治县四拨子-六拨子钼铜矿位于燕辽成矿带东部,是近年来发现的中型钼铜矿床。矿化多沿层面、裂隙充填、交代,呈脉状赋存于大红峪组的石英砂岩、长石石英砂岩及白云岩夹层和高于庄组的白云岩内,地质特征表明成矿主要与硅化关系密切。文章对矿区6个侵入岩进行了锆石LA-ICP-MS U-Pb年代学研究,结果表明,矿区存在4期岩浆侵入活动:第一期为晚三叠世(211~206 Ma),形成六柱坪和三拨子西沟细粒似斑状二长花岗岩;第二期为早侏罗世早期(196~190 Ma),形成老商家和五拨子花岗斑岩;第三期为早侏罗世晚期(177Ma),形成达子沟细粒似斑状二长花岗岩;第四期为晚侏罗世早期(160 Ma),形成七拨子粗中粒二长花岗岩。矿区辉钼矿的Re-Os加权平均年龄为(194±1)Ma,成矿时代为早侏罗世,与花岗斑岩形成时代一致(196~190 Ma),表明钼铜成矿可能与花岗斑岩岩浆期后热液活动有关。

LA-ICP-MS zircon U-Pb dating of intrusive rocks and its metallogenic significance in Sibozi-Liubozi molybdenum-copper deposit of Qinglong County, Hebei Province

Located in eastern Yanliao metallogenic belt, the Siboozi-Liubozi molybdenum-copper deposit in Qinglong County is a newly-discovered medium-sized molybdenum-copper deposit. Mineralization mainly appears in metasomatic and filling forms along bedded planes and fractures, and occurs as veins in quartz sandstone, feldspar-quartz sandstone, and dolomite intercalations in Dahongyu Formation and dolomite in Gaoyuzhuang Formation. Geological features indicate that molybdenite is closely related to silicification. Zircon LA-ICP-MS U-Pb dating of six intrusive rocks of the ore deposit was studied in this paper, and the result suggests that there exsited four stages of magmatic intrusion in the ore deposit: the first stage is the late Triassic(211~206 Ma), in which fine-grained porphyraceous monzogranite formed in Liuzhuping and Xigou of Sanbozi; the second stage is the earliest Jurassic(196~190 Ma), in which granite-porphyry formed in Laoshangjia and Wubozi; the third stage is the late early Jurassic(177 Ma), in which fine-grained porphyraceous monzogranite was produced in Dazigou; the fourth stage is the early late Jurassic(160 Ma), in which coarse-medium-grained monzogranite came into being in Qibozi. Re-Os weighted mean age of molybdenite from the ore eposit is (194±1) Ma, which is in accord with the age of the granite-porphyry(196~190 Ma), suggesting that the metallogenic epoch is early Jurassic and that Mo-Cu metallogenesis is probably related to late granite-porphyry magmatic-hydrothermal activity.