西藏邦铺钼铜多金属矿床含矿斑岩的地球化学：对成岩源区与成矿机制的启示  

Geochemical studies on ore-bearing rocks in Bangpu porphyry Mo(Cu) deposit,Tibet: Implications on the magma source and metallogenic mechanism

作　　者：胡永斌[1,2] 刘吉强[3] 胡敬仁 丁兴[5,6] 孙卫东[1,6] 刘焰[7] 凌明星[5,6] 

机构地区：[1]中国科学院广州地球化学研究所、矿物学与成矿学重点实验室,广州510640 [2]中国科学院大学,北京100049 [3]国家海洋局第二海洋研究所、国家海洋局海底科学实验室,杭州310012 [4]西藏地质调查研究院,拉萨850000 [5]中国科学院广州地球化学研究所、同位素地球化学国家重点实验室,广州510640 [6]中国科学院青藏高原地球科学卓越创新中心,北京100101 [7]中国地质科学院地质研究所,北京100037

出　　处：《岩石学报》2015年第7期2038-2052,共15页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(41090374;41421062;41172080);中国博士后科学基金(2012M511842)联合资助

摘　　要：邦铺矿床是发育于冈底斯成矿带东段的大型斑岩型钼铜矿床。其含矿岩体的岩浆源区及成矿机制依然存在争议。本次研究从含矿岩体全岩主微量元素、锆石U-Pb定年、Hf-O同位素组成等方面做了进一步的探讨。含矿石英二长斑岩年龄为13.9±0.3Ma^14.0±0.2Ma,落在冈底斯带上的其他中新世斑岩型矿床含矿岩体成岩年龄范围内。含矿岩体锆石氧同位素组成比较均一,δ18O值为4.72‰~7.22‰(均值5.99‰);锆石εHf(t)值为-2.3^+5.6。锆石原位Hf-O同位素结果表明岩浆源区具有二端元混合的特点,且主要来自亏损地幔(如MORB)组分。与驱龙斑岩铜钼矿床相比,邦铺钼铜矿床Hf-O同位素更接近陆壳端元,表明在岩浆演化过程中遭受了更多富Mo的陆壳物质的混入,因此导致了驱龙是以铜为主要成矿元素的斑岩铜钼矿床,而邦铺矿床为具有更低Cu/Mo值的斑岩型钼铜矿床。Bangpu porphyry Mo （Cu） deposit is a large Miocene Mo （Cu） deposit in Tibet. The petrogenesis of the ore-bearing Miocene intrusion and metallogenic mechanism has been debated. This study presents new results on whole rock major and trace elements, zircon U-Pb dating and Hf-O isotopic compositions of the Bangpu ore-bearing rocks. Magmatic zircons from these ore-bearing intrusions have U-Pb ages of 13.9 ± 0. 3Ma - 14.0 ±0. 2Ma, which are within the range of other Miocene porphyry deposits in Gangdese belt. Zircons from the ore-bearing rocks have δ80 ranging from 4. 72‰ ~ 7. 22‰ （ average 5.99%o） and δHI （t） from - 2. 3 to ＋ 5.6. In situ zircon Hf-O isotopic measurements for the samples yidd a binary mixing trend between mantle and continental crust, with depleted mantle-related （e. g. MORB） components as an important contributor. Compared to Qulong porphyry Cu （Mo） deposit, the zircon Hf-O isotopic measurements of Bangpu porphyry Mo （Cu） deposit plot closely to crustal end member, indicating that more continental crust melts enriched in Mo than that of Qulong deposit have been involved. These differences may be the main reason that Cu is the dominant exploitable metal （together with minor Mo） in Qulong, whereas Cu/Mo is lower than that of Qulong in Bangpu deposit.

关 键 词：邦铺 斑岩 HF-O同位素 冈底斯 

分 类 号：P588.132[天文地球—岩石学] P597.3[天文地球—地质学]