Geology, geochronology and geochemistry of the Miocene Jiaoxi quartz vein-type W deposit in the western part of the Lhasa Terrane, Tibet: Implications for ore genesis
Geology, geochronology and geochemistry of the Miocene Jiaoxi quartz vein-type W deposit in the western part of the Lhasa Terrane, Tibet: Implications for ore genesis
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DOI：
10.1016/j.oregeorev.2020.103433
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发表时间：
2020-05
影响因子：
3.3
通讯作者：
Yong Wang;Juxing Tang;Liqiang Wang;J. Huizenga;M. Santosh;Silun Zheng;Yu Hu;Teng Gao
中科院分区：
文献类型：
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作者：
Yong Wang;Juxing Tang;Liqiang Wang;J. Huizenga;M. Santosh;Silun Zheng;Yu Hu;Teng Gao
胶西矿床是拉萨地体西部发现的第一个中新世石英脉型钨矿床，含WO_3 3.9万吨。矿化赋存于含黑钨矿的热液张性石英脉中，与中新世花岗岩伴生。成矿作用可分为早期石英氧化物阶段、继之硫化物阶段和末期萤石-碳酸盐阶段。深部岩浆侵入岩包括黑云二长花岗斑岩、黑云二长花岗岩、花岗斑岩和白云母花岗岩，结晶年龄为14.5~13.7 Ma。全岩地球化学研究表明，侵入岩为富碱过铝花岗岩，经历了强烈的分离结晶作用。演化程度最高的白云母花岗岩具有较高的W、Nb和Cs含量，被认为是矿化的来源。在高分馏白云母花岗岩结晶晚期，喷出的热液流体与白云母花岗岩浆相互作用，沿伸展裂隙运移，形成胶西矿床。花岗岩中的锆石颗粒具有均匀的εHf(T)值，范围在−7.08-+3.87之间。花岗岩的初始锶同位素组成在0.7094-0.7124之间，负ε-ND(T)值在−-4.9-−-9.4之间。Sr-Nd-Hf同位素数据表明，花岗岩是壳源部分熔融的产物，岩石圈地幔的贡献很小。黑钨矿和黄铁矿的~3He/~4He比值在0.30~0.74Ra之间变化(空气的~3He/~4He=0.14×10~(-6))，证实W主要来源于地壳。区域地质、年代学和地球化学综合分析表明，中新世后碰撞过铝花岗岩及其伴生的钨矿化是由向北俯冲的印度大陆岩石圈板块的回滚和逐渐断裂触发的。演化程度较低的黑云二长花岗斑岩，含矿脉和局部云英岩蚀变，似乎与钨矿化无关。
The Jiaoxi deposit is the first Miocene quartz vein-type W deposit discovered in the western part of the Lhasa Terrane comprising with 39,000 metric tons of WO3. The mineralization occurs in wolframite-bearing hydrothermal tensional quartz veins and is associated with Miocene granites. The mineralization event can be divided into an early quartz-oxide stage succeeded by a sulfide stage, and a final fluorite-carbonate stage. Magmatic intrusions at the deposit include biotite monzogranite porphyry, biotite monzogranite, granite porphyry, and muscovite granite at depth and show crystallization ages ranging between 14.5 and 13.7 Ma. Whole-rock geochemistry shows that the intrusions are alkali-rich peraluminous granites that experienced strong fractional crystallization. The most evolved muscovite granite has high W, Nb and Cs contents and is considered to be the source for mineralization. During the late crystallization stage of the highly fractionated muscovite granite, exsolved hydrothermal fluids interacted with the muscovite granite magma and migrated along extensional fractures forming the Jiaoxi deposit. Zircon grains from the granites show uniform εHf(t) values with a wide range between −7.08 and +3.87. The granites have initial Sr isotopic compositions ranging between 0.7094 and 0.7124 and negative εNd(t) values ranging between −4.9 and −9.4. The Sr-Nd-Hf isotope data indicate that the granites were derived from partial melting of a crustal source with minor contributions from the lithospheric mantle. The3He/4He ratios for wolframite and pyrite vary between 0.30 and 0.74 Ra (Ra = 1.4 × 10–6for air), confirming that W was mainly sourced from the crust. Collectively, the regional geology, geochronology and geochemistry, indicate that the Miocene post-collisional peraluminous granites and associated W mineralization were triggered by the roll-back and gradual break-off of the northward-subducting Indian continental lithosphere slab. The less evolved biotite monzogranite porphyry, which contains ore-bearing veins and local greisen alteration, appears to be unrelated to W mineralization.