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A new Ag-polymetallic mineralisation belt was discovered parallel to the Gangdese porphyry Cu belt on the northern side of the Gangdese Range. This WE-trending belt is controlled by the Pangduo-Cuoqin thrust system. Most of the deposits occur at the junctions between the E-W-striking thrust faults and the N-S-striking tension faults. In the western part of the belt to the west of Yangbajing rift the deposits are dominated by hydrothermal vein-like Ag-Pb-Zn mineralisation and in the eastern part by skarn-type Cu-Pb-Zn-Ag mineralisation. The Ag content of ores is higher in the western belt. The deposits resulted from a hydrothermal process in the late period of continental collisional orogenic activity or in the early stage of collision-extension., A new Ag-polymetallic mineralisation belt was discovered parallel to the Gangdese porphyry Cu belt on the northern side of the Gangdese Range. This WE-trending belt is controlled by the Pangduo-Cuoqin thrust system. Most of the deposits occur at the junctions between the E-W-striking thrust faults and the N-S-striking tension faults. In the western part of the belt to the west of Yangbajing rift the deposits are dominated by hydrothermal vein-like Ag-Pb-Zn mineralisation and in the eastern part by skarn-type Cu-Pb-Zn-Ag mineralisation. The Ag content of ores is higher in the western belt. The deposits resulted from a hydrothermal process in the late period of continental collisional orogenic activity or in the early stage of collision-extension.

Available data indicate that there have been at least two stages of tectonic evolution since the Miocene in the Tibetan plateau, which is now tectonically in a post-collisional stage. Mineralisation during the post- collisional periods has produced a variety of significant mid-Miocene deposits including the porphyry Cu deposits and the associated skarn Ag- Pb-Zn deposits along the Gangdese batholiths, the epithermal Sb-Au deposits in southern Tibet, the hydrothermal vein-type and skarn-type Ag- Pb-Zn deposits to the north of the Gangdese porphyry Cu belt and modern Cs-Au deposits related to hot-spring activity in the Tibetan plateau., Available data indicate that there have been at least two stages of tectonic evolution since the Miocene in the Tibetan plateau, which is now tectonically in a post-collisional stage. Mineralisation during the post- collisional periods has produced a variety of significant mid-Miocene deposits including the porphyry Cu deposits and the associated skarn Ag- Pb-Zn deposits along the Gangdese batholiths, the epithermal Sb-Au deposits in southern Tibet, the hydrothermal vein-type and skarn-type Ag- Pb-Zn deposits to the north of the Gangdese porphyry Cu belt and modern Cs-Au deposits related to hot-spring activity in the Tibetan plateau.

The tectonic evolution of the Tibetan orogen is divided into syn- collisional, late-collisional and post-collisional periods. The orogeny during the late-collisional period was characterised by intra-continental subduction, crustal shortening, large-scale thrusting and strike-slip faulting systems which developed in the margins of the Tibetan plateau, and resulted in the development of potassic porphyry stocks and carbonatite-alkalic complexes in eastern Tibet and potassic-ultrapotassic volcanic rocks in northern Tibet. Four significant metallogenic events occurred in the eastern margin of the Tibetan plateau, porphyry Cu-Mo(- Au) mineralisation related to a large-scale strike-slip faults system, REE mineralisation associated with carbonatite-alkalic complexes which formed the Mianning-Dechang REE belt in western Sichuan, Pb-Zn-Ag mineralisation controlled by thrust faulting systems, forming at least two large Pb-Zn-Ag deposits in the Lanping strike-slip pull-apart basin, western Yunnan, and Au mineralisation related to large-scale shearing, which produced shear- or orogenic-type Au deposits in western Sichuan and Yunnan., The tectonic evolution of the Tibetan orogen is divided into syn- collisional, late-collisional and post-collisional periods. The orogeny during the late-collisional period was characterised by intra-continental subduction, crustal shortening, large-scale thrusting and strike-slip faulting systems which developed in the margins of the Tibetan plateau, and resulted in the development of potassic porphyry stocks and carbonatite-alkalic complexes in eastern Tibet and potassic-ultrapotassic volcanic rocks in northern Tibet. Four significant metallogenic events occurred in the eastern margin of the Tibetan plateau, porphyry Cu-Mo(- Au) mineralisation related to a large-scale strike-slip faults system, REE mineralisation associated with carbonatite-alkalic complexes which formed the Mianning-Dechang REE belt in western Sichuan, Pb-Zn-Ag mineralisation controlled by thrust faulting systems, forming at least two large Pb-Zn-Ag deposits in the Lanping strike-slip pull-apart basin, western Yunnan, and Au mineralisation related to large-scale shearing, which produced shear- or orogenic-type Au deposits in western Sichuan and Yunnan.

The main collisional event lasted about 25 Ma from 65 Ma to 41 Ma and resulted in the formation of the main part of the orogenic belt. At least four important ore-forming events occurred during the main collisional orogenic epoch, including the Sn and rare metal event related to crust- derived granite, forming the Tengchong Sn and rare metal ore concentration area in the east Tibetan plateau, the Cu-Au-Mo event related to crust/mantle-derived granite, forming a Cu-Au ore belt 100 km long in south Gangdese, the shear zone Au event, forming the potential Au belt along the Yarlung Zangbo suture zone, and the Cu-Au event related to crust uplift, forming porphyry/epithermal transitional type Cu-Au deposits represented by the Xiongcun deposit., The main collisional event lasted about 25 Ma from 65 Ma to 41 Ma and resulted in the formation of the main part of the orogenic belt. At least four important ore-forming events occurred during the main collisional orogenic epoch, including the Sn and rare metal event related to crust- derived granite, forming the Tengchong Sn and rare metal ore concentration area in the east Tibetan plateau, the Cu-Au-Mo event related to crust/mantle-derived granite, forming a Cu-Au ore belt 100 km long in south Gangdese, the shear zone Au event, forming the potential Au belt along the Yarlung Zangbo suture zone, and the Cu-Au event related to crust uplift, forming porphyry/epithermal transitional type Cu-Au deposits represented by the Xiongcun deposit.

A study and comparison of three major porphyry copper belts suggests that the rock with most potential for porphyry deposits is not typical of arc magmas but rich in SiO2, Al2O3 and Sr and poor in Y. In the Andean orogenic belt, such adakitic magmas were apparently derived from direct melting of subducted oceanic crust which then underwent fractionation. In the collisional orogenic belts of Tibet, partial melting of old oceanic crust metamorphosed to eclogite gave rise to adakitic magmas that mixed with mantle melts to produce the Gandese and Yulong porphyry Cu systems., A study and comparison of three major porphyry copper belts suggests that the rock with most potential for porphyry deposits is not typical of arc magmas but rich in SiO2, Al2O3 and Sr and poor in Y. In the Andean orogenic belt, such adakitic magmas were apparently derived from direct melting of subducted oceanic crust which then underwent fractionation. In the collisional orogenic belts of Tibet, partial melting of old oceanic crust metamorphosed to eclogite gave rise to adakitic magmas that mixed with mantle melts to produce the Gandese and Yulong porphyry Cu systems.

There are two parallel metallogenic belts in the eastern Gangdese Mountains: porphyry Cu to the south and Cu-polymetallic to the north. Re-Os dating of molybdenite from Bangpu in the north belt yields an age identical to that of the porphyry deposits, suggesting a relationship and that porphyry mineralisation must have played a dominant role in metallogenic events in the Gangdese belts. Different types of porphyry-related deposit are attributable to the different surroundings into which the porphyries intruded: almost all the known Cu-Mo deposits are in the south whereas Cu-Pb-Zn deposits are mostly in the north., There are two parallel metallogenic belts in the eastern Gangdese Mountains: porphyry Cu to the south and Cu-polymetallic to the north. Re-Os dating of molybdenite from Bangpu in the north belt yields an age identical to that of the porphyry deposits, suggesting a relationship and that porphyry mineralisation must have played a dominant role in metallogenic events in the Gangdese belts. Different types of porphyry-related deposit are attributable to the different surroundings into which the porphyries intruded: almost all the known Cu-Mo deposits are in the south whereas Cu-Pb-Zn deposits are mostly in the north.

A study of Sahentuohai and Dashankou, two typical gold deposits, shows that they are controlled by brittle-ductile shear zones. Two types of gold ore can be distinguished, one consisting mainly of auriferous mylonites with small amounts of sulphides and the other the quartz vein type. The main styles of host-rock alteration are silicification, sericitisation and ferrodolomitisation. A study of fluid inclusions and stable isotopes indicates that formation temperatures ranged from 170 to 460 degrees C and pressures from 0.94 to 32.2 MPa; the mineralising fluids were mixtures of a deep-seated source ore solution, a magmatic solution and underground water., A study of Sahentuohai and Dashankou, two typical gold deposits, shows that they are controlled by brittle-ductile shear zones. Two types of gold ore can be distinguished, one consisting mainly of auriferous mylonites with small amounts of sulphides and the other the quartz vein type. The main styles of host-rock alteration are silicification, sericitisation and ferrodolomitisation. A study of fluid inclusions and stable isotopes indicates that formation temperatures ranged from 170 to 460 degrees C and pressures from 0.94 to 32.2 MPa; the mineralising fluids were mixtures of a deep-seated source ore solution, a magmatic solution and underground water.