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西藏冈底斯北缘发育一条矽卡岩型Fe-Cu-Pb-Zn多金属成矿带,列廷冈-勒青拉矿床是这条带上同时发育Fe-Cu-Pb-Zn四个矿种的最具代表性矿床。矿区内Fe-Cu矿体位于列廷冈矿段和勒青拉矿段东侧,Pb-Zn矿体位于勒青拉矿段西侧,与成矿作用相关的居布扎日岩体位于矿区东南部,呈复式岩体,以大面积岩基产状出露。岩体北侧列廷冈Fe-Cu-(Mo)矿段的花岗闪长斑岩锆石U-Pb年龄为62.85±0.58 Ma,为印度-欧亚大陆碰撞造山带主碰撞早期岩浆活动的产物。岩石地球化学分析表明该套岩石属于高钾钙碱性、准铝质向过铝质过渡花岗岩;其Rb、Ba、Th、U、Pb等大离子亲石元素(LILE)强烈富集,Nb、Ta、Ti、P等高场强元素(HFSE)和Sr强烈亏损;稀土总量变化于173.23×10-6~208.98×10-6之间,(La/Yb)N介于5.71~6.24之间,具有中等负Eu异常(0.45~0.54),富集轻稀土元素(LREE),相对亏损重稀土元素(HREE);总体具有弧火山岩的地球化学特征。锆石结晶温度平均为693℃,岩体的氧逸度较小,平均为-8.63,表明其岩浆经历了在水近饱和条件下发生的熔融过程。锆石176 Hf/177 Hf=0.282557~0.282927,εHf(t)=-6.25~6.79,平均地壳模式年龄TDMC=696~1522 Ma,表明成矿岩体岩浆源区具有幔源岩浆混染壳源岩浆特征,这也成为形成矽卡岩型Fe-Cu-Pb-Zn多金属矿化共存的主导因素。结合前人及本次研究结果,建立冈底斯北亚带Fe-Cu-Pb-Zn多金属矿化成矿过程如下:在印-亚大陆碰撞造山带主碰撞早期,俯冲的新特提斯洋板片发生回卷引起软流圈地幔上涌,诱发楔形地幔区部分熔融,经MASH过程产生的幔源岩浆上侵,并在部分地区遭受与壳源岩浆的混染甚至混合。当幔源岩浆与壳源岩浆分别上侵并与碳酸盐岩地层相互作用时,矿区形成矽卡岩型Fe-Cu和矽卡岩型Pb-Zn矿化,但当壳幔混源的岩浆上侵并与碳酸盐岩地层相互作用时,矿区则形成矽卡岩型Fe-Cu-Pb-Zn等多金属矿化。
A skarn-type Fe-Cu-Pb-Zn polymetallic metallogenic belt is developed in the northern margin of the Gangdise area in Tibet. The Litingng-Leqala deposit is the site where four Fe-Cu-Pb-Zn deposits The most representative of the deposit. The Fe-Cu orebody in the mining area is located on the east side of the Litinggang ore section and the Leqingla ore section, and the Pb-Zn orebody is located on the west side of the Leqingzala ore section. The Juzhazijin massif associated with mineralization is located in the mining area Southeastern, was a compound rock, with a large area of rock-like outcrops. The zircon U-Pb age of the granodiorite porphyry in the Fe-Cu- (Mo) ore section of the Litingingtang of the northern side of the rock mass is 62.85 ± 0.58 Ma, which is the magmatic activity of the main collision of the Indo-Eurasia continental collision orogen product. The lithogeochemical analysis shows that the rocks belong to the high-K calc-alkaline and quasi-aluminous to peridotite transitional granites. The LILEs such as Rb, Ba, Th, U and Pb are strongly enriched, while the Nb, The contents of HFSE and Sr in Ta, Ti and P are strongly depleted. The total amount of REEs varies from 173.23 × 10-6 to 208.98 × 10-6, while La / Yb is between 5.71 and 6.24 , With moderate negative Eu anomalies (0.45-0.54), enrichment of LREE and relatively depleted heavy rare earth elements (HREEs), and generally have the geochemical characteristics of arc volcanic rocks. The average crystallization temperature of zircon is 693 ℃, and the oxygen fugacity of the rock mass is small, averaging -8.63, indicating that the magma underwent a melting process under water saturation. The average crustal model age is from 696 to 1522 Ma, indicating that the magma source rocks of the ore-forming bodies have mantle-derived magma-derived crustal magma Features, which also became the dominant factor for the formation of skarn-type Fe-Cu-Pb-Zn polymetallic mineralization coexistence. Based on the previous studies and the results of this study, the mineralization process of Fe-Cu-Pb-Zn polymetallic mineralization in the northern Gangdese subzone is established as follows: During the main collision of the Indian-Continental collision orogen, the subducted Neo-Tethys Ocean Rewinding of the slab caused upwelling of the mantle due to asthenosphere, induced partial melting of the wedge-shaped mantle zone, mantle-derived magma resulting from the MASH process invaded and in some areas were mixed with or even mixed with the crustal magma. When mantle-derived magma and crustal magma respectively invaded and interacted with carbonate rocks, skarn Fe-Cu and skarn-type Pb-Zn mineralization were formed in the ore district. However, When invaded and interacted with carbonate stratum, the ore area formed skarn-type Fe-Cu-Pb-Zn and other polymetallic mineralization.