新疆索尔库都克铜钼矿床含矿粗面英安斑岩岩石学、地球化学特征与岩石成因

Petrology, geochemistry and petrogenesis of the ore-bearing trachydacite porphyry from the Suoerkuduke Cu-Mo deposit, Xinjiang, NW China

位于东准噶尔北缘的索尔库都克铜钼矿床,一直以来被认为属于一个与辉石闪长玢岩有关的层控夕卡岩型矿床。笔者在矿区露天采场及勘探钻孔调查中发现该矿床的成矿母岩可能为粗面英安斑岩,粗面英安斑岩多发育脉状和浸染状铜、钼矿化,且由浅部到深部热液活动逐渐加强,显示其与成矿关系密切;粗面英安斑岩的K2O+N2O为9.38%~10.3%、K2O/Na2O为2.63~3.17、A/CNK为0.89~0.98,属准铝质、富钾碱性岩系列,为I型花岗岩;微量元素方面,相对富集Rb、Ba和K等大离子亲石元素和强不相容元素(如U和Th),有明显Sr、Ti、Nb和Ta的亏损,与岛弧型花岗岩的特征一致;粗面英安斑岩的(87Sr/86Sr)i为0.70100~0.70384,(143Nd/144Nd)i为0.512387~0.512436,εNd(t)为(+4.8^+5.8),T2DM为663~741 Ma,显示其可能源于地幔楔部分熔融。

The Suoerkuduke Cu-Mo deposit is located in the northeastern margin of East Junggar. It was traditionally regarded as a stratabound skarn deposit associated with pyroxene andesite porphyrite. Based on investigation of open-pit and the exploration borehole in the mining area, this paper considers that the host rock of this deposit may be the trachydacite porphyry, evidenced by that the trachydacite porphyry developed veinlet copper and molybdenum mineralization, and the hydrothermal activity became much stronger from the shallow to deep. The K20＋Na20 content in fresh trachydacite porphyry reaches 9.38%-10.3%, the K20/Na20 value is 2.63-3.17, and its A/CNK value is 0.91-1.04, indicating that the trachydacite porphyry belongs to the metaluminous and high-K calc-alkaline rock series being affinity of ＂I＂ type granite. The geochemistry of enriching in large-ion lithophile elements （LILE, such as Rb, Ba and K） and strong incompatible elements （such as U, and Th）, relatively depleting in high field strength elements （HFSE, such as Sr, Nb, Ta and Ti） suggest that the trachydacite porphyry may display a characteristics of the arc magma. The isotope characterized by （S7Sr/S6Sr）i ratio of 0.70100-0.70384, （143Nd/144Nd）irati of 0.512387-0.512436, end（t） value of ＋4.8- ＋5.8, and young Nd two-stage model age of 663-741 Ma, indicate that the trachydacite porphyry may be derived from the partial melting of mantle wedge.