华南地质与矿产
華南地質與礦產
화남지질여광산
Geology and Mineral Resources of South China
2015年
3期
236-245
,共10页
石英斑岩%锆石U-Pb年龄%Hf同位素%成因机制%湖南七宝山
石英斑巖%鋯石U-Pb年齡%Hf同位素%成因機製%湖南七寶山
석영반암%고석U-Pb년령%Hf동위소%성인궤제%호남칠보산
quartz-porphyry%zircon U-Pb dating%Hf isotopes%petrogenesis%Qibaoshan Cu-polymetallic de-posit
湖南浏阳七宝山铜多金属矿床位于钦杭成矿带西南段，是湘东北规模最大的铜多金属矿床，矿区内的石英斑岩对成矿贡献非常大。石英斑岩内锆石具有典型岩浆期锆石特征，LA-ICP-MS U-Pb定年结果为154.8依1.8 Ma，代表其形成年龄，属晚侏罗世岩浆活动产物。岩浆期锆石的176Hf/177Hf=0.282120~0.282539，对应的εHf(t)值均为负值，集中在-19.8~-4.9，计算的亏损地幔模式年龄（tDM1）集中在1001~1596 Ma，平均地壳模式年龄（tDM2）集中于1519~2450 Ma，表明石英斑岩的岩浆源区具有明显壳源特征，来自于古元古代至中元古代地壳的部分熔融。结合岩石学研究，七宝山矿区内石英斑岩体成因可能是在华南地块受到伊泽奈奇（Izanagi）板块向西北俯冲的影响下，古元古代至中元古代地壳部分熔融形成岩浆，而后岩石圈拆沉和软流圈物质上涌进入岩浆发生不均匀混合在晚侏罗世上侵形成的。
湖南瀏暘七寶山銅多金屬礦床位于欽杭成礦帶西南段，是湘東北規模最大的銅多金屬礦床，礦區內的石英斑巖對成礦貢獻非常大。石英斑巖內鋯石具有典型巖漿期鋯石特徵，LA-ICP-MS U-Pb定年結果為154.8依1.8 Ma，代錶其形成年齡，屬晚侏囉世巖漿活動產物。巖漿期鋯石的176Hf/177Hf=0.282120~0.282539，對應的εHf(t)值均為負值，集中在-19.8~-4.9，計算的虧損地幔模式年齡（tDM1）集中在1001~1596 Ma，平均地殼模式年齡（tDM2）集中于1519~2450 Ma，錶明石英斑巖的巖漿源區具有明顯殼源特徵，來自于古元古代至中元古代地殼的部分鎔融。結閤巖石學研究，七寶山礦區內石英斑巖體成因可能是在華南地塊受到伊澤奈奇（Izanagi）闆塊嚮西北俯遲的影響下，古元古代至中元古代地殼部分鎔融形成巖漿，而後巖石圈拆沉和軟流圈物質上湧進入巖漿髮生不均勻混閤在晚侏囉世上侵形成的。
호남류양칠보산동다금속광상위우흠항성광대서남단，시상동북규모최대적동다금속광상，광구내적석영반암대성광공헌비상대。석영반암내고석구유전형암장기고석특정，LA-ICP-MS U-Pb정년결과위154.8의1.8 Ma，대표기형성년령，속만주라세암장활동산물。암장기고석적176Hf/177Hf=0.282120~0.282539，대응적εHf(t)치균위부치，집중재-19.8~-4.9，계산적우손지만모식년령（tDM1）집중재1001~1596 Ma，평균지각모식년령（tDM2）집중우1519~2450 Ma，표명석영반암적암장원구구유명현각원특정，래자우고원고대지중원고대지각적부분용융。결합암석학연구，칠보산광구내석영반암체성인가능시재화남지괴수도이택내기（Izanagi）판괴향서북부충적영향하，고원고대지중원고대지각부분용융형성암장，이후암석권탁침화연류권물질상용진입암장발생불균균혼합재만주라세상침형성적。
The Qibaoshan Cu-polymetallic deposit in Liuyang is belong to the west section of Qinzhou-Hangzhou metallogenic belt,and it is the largest Cu-polymetallic deposit in northeastern Hunan Province. The quartz-porphyry is on a great contribution of the mineralization of the Qibaoshan Cu-polymetal-lic deposit. The zircons from quartz-porphyry are typical magmatic zircons. LA-ICP-MS U-Pb dating of the zircons shows the age of 154.8±1.8 Ma, which represents the crystallization age of quartz-porphyry, and indi-cate it was Late Mesozoic intrusion. The new born zircons have intermediate 176Hf/177Hf of 0.282120 ~0.282539,εHf (t) of-19.8~-4.9, model age of crust tDM2 from 1519 to 2450 Ma, indicating that the rock was formed by the partial melting of the Paleoproterozoic to Mesoproterozoic crust. Through the comprehensive study of crystallization age and Hf isotope model age of the zircons, the crustal magma formed the quartz-por-phyry was from a mixed magma from the crust source and the mantle source or form a mixed magma with the characteristics of the depleted mantle, which may containing the very old continental crust (the Hadean crust). In 175 ~ 145 Ma, an extensive rocks related to the porphyry and skarn copper deposit intruded of Qinzhou-hangzhou metallogenic belt. And these rocks were the product of the heyday of the system of temper-ature increasing and pressure depressing after the Izanagi Plate subducting toward northwest into the South China Block. The study of the geochemical characteristics of the quartz-porphyry before shows that the magma also having the the mantle source. All these data suggest the magma from the partial melting material of Paleo-proterozoic to Mesoproterozoic crust or even much older crust was in the magma chamber already, the as-thenospheric mantle fluid upwelling into the magma chamber and they mixed inhomogenously by the effects of the delamination of lithosphere and asthenosphere upwelling. And then the magma intruded upward to form the quartz porphyry.
