Type, indicator, mechanism, model and relationship with mineralization of magma mixing: A case study in North Xinjiang
岩浆混合作用的类型、标志、机制、模式及其与成矿的关系——以新疆北部为例

Magma mixing rockbodies are widely developed in the North Xinjiang. The sorts of rockbody can be classified into three types: calc-alkaline granitoid, alkali-feldspar granite and alkali granite, among which the first type is dominant. The microgranular enclaves type is dominantly dioritic having viarable composition from diorite, quartz diorite, quartz monzodiorite to granodiorite, with gabbro, andesitic basalt and andesitic porphyrite in some cases. Even magma-mixed rocks occur in some area. Magma mixing in the study area develops in four geological/tectonic stages: ocean-continent subduction stage in D3-C1, continent-continent collision stage in C1-C2, post-collision stage in C2-P2 and intra-plate stage in T1. Discriminated indicators for magma mixing can be summed up as rockbody occurrence (e.g. in roughly equiaxial shape), field indicator (e.g. presence of various MME and occasional magma-mixed rocks), microscopic indicator (e.g. quenching and petrographic disequilibrium texture), geochemical indicator (e.g. linear and transition composition and geochemical parameter), and geochronology indicator (accordant age of related rocks). It is speculated that the magma mixing in North Xinjiang should be multi grades/orders, and the deep mixing of magma source behaves as crust-mantle mixing. The magma mixing mechanism and model are characterized by multi-stages, injected manner of acid magma by basic magma, and sequential physic-chemic mixing. It is closely relevant to porphyry Cu-Mo-Au mineralization, as the model that basic-acid mixed magmas evolve to ore-bearing magma through differentiation. Therefore, the prospecting indicator for the porphyry deposit in North Xinjiang may be ascribed to that the late supplying intruded small porphyry stock neighboring, surrounding and within magma mixing granitoid batholith.