摘要:
位于准噶尔西北缘萨吾尔地区的罕哲尕能Cu-Au矿床是新近发现的斑岩型矿床,具有很好的找矿前景。矿区岩浆活动早期以闪长岩为主,晚期以花岗闪长岩和二长花岗斑岩为主。钻孔中所见似斑状石英二长岩LA-ICP-MS锆石U-Pb年龄为343.6±5.7Ma~345.3±8.3Ma;二长花岗斑岩锆石U-Pb年龄为334.9±7.3Ma~336.4±7.5Ma,表明西准萨吾尔地区早石炭世存在一期重要的岩浆-热液Cu-Au成矿事件。花岗闪长岩、石英二长岩、闪长玢岩、闪长岩和二长花岗斑岩的主量元素具有一致的演化趋势,表明它们可能是 同一岩浆演化的产物。富集大离子亲石元素(LILE:如Rb、Ba、K、Sr)和活泼的不相容元素(如:U、Th),相对亏损高场强元素(HFSE:如Nb、Ta、Ti),显示具有岛弧岩浆的地球化学特征。87Sr/86Sri比值在0.7033~0.7037之间,143Nd/144Nd比值在0.512538~0.512579之间,εNd(t)在+6.7~+7.5之间,显示源区具有类似亏损地幔的特征;而且具有年轻的Nd两阶段模式年龄为488~553Ma,这些特征表明罕哲尕能矿区岩石的岩浆源区可能来源于亏损地幔分异的新生玄武质下地壳。罕哲尕能Cu-Au矿床的形成时代明显早于该区域A型花岗岩的形成时代(290~300Ma左右),结合岩石微量元素特征反映其形成于岛弧构造背景,萨吾尔山具有寻找斑岩Cu-Au矿的成矿条件。
Abstract:
Hanzheganeng Cu-Au deposit, located in northwestern margin of Junggar, is a newly discovered porphyry copper deposit with great potential. Magmatic emplacement activity is mainly diorite in the early stage, and is mainly granodiorite and moznogranite porphyry in the late stage. Porphyraceous quartz monzonite yields a LA-ICP-MS zircon U-Pb age of 343.6±5.7Ma~345.3±8.3Ma, and monzogranite porphyry yields a zircon age of 334.9±7.3Ma~336.4±7.5Ma. These ages indicate that there is an Early Carboniferous important magmatic-hydrothermal Cu-Au mineralization event in Sawuer region of West Junggar. Major elements of granodiorite, quartz monzonite, diorite porphyrite, diorite, and monzogranite porphyry show a consistent evolution trend, indicating that they may be the product of the same magmatic evolution. And their geochemical characteristics of enriching in large-ion lithophile elements (LILE: such as Rb, Ba, K, Sr) and more mobile incompatible elements (such as: U, Th), relatively depleting in high field strength elements (HFSE: such as Nb, Ta, Ti) show that they have the characteristics of arc magma. Their isotopic characteristics with 87Sr/86Sri ratio of 0.7033~0.7037, 143Nd/144Nd ratio of 0.512538~ 0.512579, εNd(t) value of +6.7~+7.5, indicate their magma source is an analogy of the depleted mantle. And they have young Nd two-stage model age of 488~553Ma, indicating that Hanzheganeng magmatic rocks may be derived from juvenile basaltic lower crust differentiated from the depleted mantle source. The formation age of Hanzheganeng Cu-Au deposit is significantly earlier than the formation age of A-type granites (290~300Ma) in this region, combined with trace element characteristics, suggest this deposit was formed in accretional arc setting, and Sawuer district have favorable metallogenetic conditions for porphyry Cu-Au deposits.
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