Magma mixing characteristics and geological significance of host porphyry from the aolunhua Mo-Cu deposit, inner mongolia

作者：Zou Tao; Wang Yu Wang^*; Wang Jing Bin; Yuan Ji Ming; Lin Long Jun; Liao Zhen

来源：Journal of Jilin University (Earth Science Edition), 2012, 42(SUPPL.2): 171-187.

• Aolunhua intrusion
• Continental crusts
• Geological significance
• Host rocks
• Inner Mongolia
• Isotopic signatures
• Mafic enclaves
• Magma mixing
• Major oxides
• Porphyry deposits
• REE pattern
• Silicic magmas
• Source region
• Underplating

A large number of mafic enclaves are widely distributed in the host porphyry of Aolunhua porphyry Mo-Cu deposit, Inner Mongolia. These mafic enclaves are mainly dioritic, elliptic in shape and are of microgranular and igneous-texture. Under microscope, the acicular apatite and eyeball-shape quartz with mafic minerals selvage are developed in the enclaves. These enclaves have captured lots of corroded and recrystallized plagioclase, quartz, biotite phenocrysts from host rock. All these characteristics indicate an obvious magma mixing genesis of the mafic enclaves. Geochemically these mafic enclaves are more basic than their host rocks, and the major oxides of the mafic enclaves and the host rocks are plotted on same a linear trend. The REE pattern, trace element and isotopic signatures of the dioritic enclaves and of the magma-mixed rocks are similar to those of the host granites, which suggest that exchanges of elements occurred between the enclaves and the host rocks. Consilient single-zircon U-Pb age of (134.1±1.4) Ma from the host rock and (133.6±1.0)Ma from the mafic enclaves also prove that the mafic enclaves is the product of magma mixing. The Sr, Nd isotopic results show that the source region of Aolunhua intrusion was a immature continental crust source. The primary magma of the mafic enclaves was more basic before its mixing with the more silicic magma and could be derived from the mantle. Discovery of magma mixing in Aolunhua porphyry deposit may be the direct evidence of mantle-derived magma underplating in the region.

• 出版日期2012