In this paper an integrated geological and geochemical comparison is made of Carlin-type and Carlin-like-type gold deposits in the region of South Qinling with their associated hydro-thermal sedimentary lead-zinc depo...In this paper an integrated geological and geochemical comparison is made of Carlin-type and Carlin-like-type gold deposits in the region of South Qinling with their associated hydro-thermal sedimentary lead-zinc deposits, the Carlin-type deposits in the Yunnan-Guizhou-Guan-gxi gold triangle, China, the Carlin gold deposits, Carlin, western United States, and the Mu-runtau-type gold deposits in Uzbekistan. The comparative study indicates that the formation ofthese deposits has an intimate coupling relation with the mechanism of the tectonic movement ofmodern plates. Therefore, these deposits belong to those that were formed in the orogenic stage.They have the following similar characteristics: they are all sediment-hosted, occur in a tectonicenvironment of extensional rifting nature and show the characteristics of syngenetically modifiedmineralization. On the other hand, they also have noticeable differences: they are different inrespect to their tectonic settings, association and structure of orogenic belts and complexity andstrength of the modified mineralization. The regional tectonic evolution and extensive mineraliza-tion in orogenic belts are different expressions of the same continental dynamic process.展开更多
There exist intermediate to intermediate-acid shoshonitic rocks dated at 26.3- 36.7Ma in the Early Tertiary extensional basins along the NE flank of the Dali-Jianchuan section of the Honghe-Ailaoshan left-lateral stri...There exist intermediate to intermediate-acid shoshonitic rocks dated at 26.3- 36.7Ma in the Early Tertiary extensional basins along the NE flank of the Dali-Jianchuan section of the Honghe-Ailaoshan left-lateral strike-slip ductile shear zone, where some high- and medium-high grade metamorphosed mafic enclaves have been found. According to the P-T conditions and mineral assemblage characteristics, the enclaves are grouped into three types: type-Ⅰ, garnet diopsidite, formed at lower crust or in the transitional section between the mantle and the crust with the metamorphic condition P=(10.47-11.51)×108 Pa and T=771-932℃; type-Ⅱ, garnet- and diopside-bearing amphibolite, formed at the depth of middle to lower crust with the metamorphic condition: P=(6-10) ×108 Pa and T=780-830℃; type-Ⅲ, metamorphosed gabbro, formed at relatively higher levels than the above 2 types with lower metamorphic condition. Type-Ⅰand type-Ⅱenclaves had experienced a decompressional retrograde metamorphism caused by tectonic elevation associated with the metasomatism of SiO 2, Na 2O-rich fluid phase with the new equilibrated temperature at T=761-778℃. Geochemical evidence indicates that both deep-derived mafic enclaves and host rocks have similar EM Ⅱ properties, which are related to the involvement of subducted materials. The sustaining subduction, compression and strike-slip ductile shearing between the India plate and the Yangtze craton are the main constraints on the subcontinental mantle properties, interaction between crust and mantle, and the formation and evolution of alkali-rich magma.展开更多
基金Provincial Natural Science Foundation of Shaanxi, China
文摘In this paper an integrated geological and geochemical comparison is made of Carlin-type and Carlin-like-type gold deposits in the region of South Qinling with their associated hydro-thermal sedimentary lead-zinc deposits, the Carlin-type deposits in the Yunnan-Guizhou-Guan-gxi gold triangle, China, the Carlin gold deposits, Carlin, western United States, and the Mu-runtau-type gold deposits in Uzbekistan. The comparative study indicates that the formation ofthese deposits has an intimate coupling relation with the mechanism of the tectonic movement ofmodern plates. Therefore, these deposits belong to those that were formed in the orogenic stage.They have the following similar characteristics: they are all sediment-hosted, occur in a tectonicenvironment of extensional rifting nature and show the characteristics of syngenetically modifiedmineralization. On the other hand, they also have noticeable differences: they are different inrespect to their tectonic settings, association and structure of orogenic belts and complexity andstrength of the modified mineralization. The regional tectonic evolution and extensive mineraliza-tion in orogenic belts are different expressions of the same continental dynamic process.
文摘There exist intermediate to intermediate-acid shoshonitic rocks dated at 26.3- 36.7Ma in the Early Tertiary extensional basins along the NE flank of the Dali-Jianchuan section of the Honghe-Ailaoshan left-lateral strike-slip ductile shear zone, where some high- and medium-high grade metamorphosed mafic enclaves have been found. According to the P-T conditions and mineral assemblage characteristics, the enclaves are grouped into three types: type-Ⅰ, garnet diopsidite, formed at lower crust or in the transitional section between the mantle and the crust with the metamorphic condition P=(10.47-11.51)×108 Pa and T=771-932℃; type-Ⅱ, garnet- and diopside-bearing amphibolite, formed at the depth of middle to lower crust with the metamorphic condition: P=(6-10) ×108 Pa and T=780-830℃; type-Ⅲ, metamorphosed gabbro, formed at relatively higher levels than the above 2 types with lower metamorphic condition. Type-Ⅰand type-Ⅱenclaves had experienced a decompressional retrograde metamorphism caused by tectonic elevation associated with the metasomatism of SiO 2, Na 2O-rich fluid phase with the new equilibrated temperature at T=761-778℃. Geochemical evidence indicates that both deep-derived mafic enclaves and host rocks have similar EM Ⅱ properties, which are related to the involvement of subducted materials. The sustaining subduction, compression and strike-slip ductile shearing between the India plate and the Yangtze craton are the main constraints on the subcontinental mantle properties, interaction between crust and mantle, and the formation and evolution of alkali-rich magma.
