| 内蒙古哈达庙含金隐爆角砾岩带地质特征及成因探讨 |
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| GEOLOGICAL CHARACTERISTICS AND ORIGIN OF THE HADAMIO GOLD-BEARING CRYPTOEXPLOSION BRECCIA ZONE,NEI MONGGOL |
| Situated in the Xianghuangqi syclinorium of Tianshan-Nei Monggol fold belt formed during the late Hercynian orogenesis, the Hadmio gold-bearing cryptoexplosion breccia zone is mainly controlled by a NE or WE-trending structure line. It consists of 33 breccia dikes (or vein) and tourmaline fissure vein groups. The breccia dikes and fissure veins, some of which contain native gold, are commonly from tens to several hundreds meters long, the longest one being 650 m. They are usually from 1 to 4 m wide and may be up to 6 m in width. The rock fragmets of the dikes are mostly granodiorite and granodiorite porphyry. The matrix in the breccia may be divided into three types, i. e. altered mineral assemblage, mineral and rock fragments and metal sulfids, of which the sulfides are closely associated with gold mineralization.The result of isotope study shows that breccia dikes are characterized by: δ34S, 2.8‰ δD, -46‰; δ18OH2O 2.4‰ and 87Sr/86Sr, 0.7088. The REE pattern of the whole breccia rock exhbits a rightward decline curve with the δEu value of 0.34. The REE content, LREE/HREE and δEu of the cementation are lower than those of the rock fragment in the breccia dike, which has similar REE pattern to that of granodiorite in the area.On the basis of the above mentioned facts, it may be considered that the granitic rocks and breccia were originated from the anatexis of crustal rocks. They are resulted from the different evolutional stages of comagmatic sources. When cryptoexplosion and boiling of granitic melt took place, the P, T, pH and fO2 conditions were changed and gold were deposited as native gold, electrum and gold-bearing pyrite in the breccia dikes. |
| NIE Feng-jun,ZHANG Hong-tao,SUN Hao,FAN Jian-yan.1991.GEOLOGICAL CHARACTERISTICS AND ORIGIN OF THE HADAMIO GOLD-BEARING CRYPTOEXPLOSION BRECCIA ZONE,NEI MONGGOL[J].Acta Geoscientica Sinica,12(1):81-90. |
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