ANALYSIS ON GOLD AND COPPER ORE-FORMING SYSTEM WITH COLLISION OROGENY OF EASTERN TIANSHAN

According to tectono stratigraphical division principle, different units in Kangguertage Huangshan collision zone, Eastern Tianshan, are divided into order and disorder two types of stratum rock associations, which belong to two kinds of different tectono volcanic activity belts. The collision ororeny and ductile shear zone have a strong space time coupling. Based on the island arc bearing volcanic rock on both sides of the collision zone, time of ore forming and rock forming, characteristics of collision granit, geochemical province, special multistage collision orogeny and intracontinental orogeny basin forming developed features have been found. Gold and copper deposits, with the relation to the collision orogeny, are divided into seven genetic types. The ten metallogenic zones are classified into two kinds of ore forming system of paleo continental margin. Metallogenesis of gold deposits can be classified into five stages. Gold and copper deposits are distributed in belts with the relation to the development of the collision orogeny. The distribution of main large scale copper deposits in the north part of the collision zone and most large middle scale gold deposits in the south part of the collision zone can direct the prospecting for gold and copper deposits. The actual targets are put forward.

Study of tectonic layering motion and layering mineralization in the Tongling metallogenic cluster

Analysis of the deep tectonics and cover tectonic deformations shows that tectonic layering motion is a typical lithospheric characteristic in the Tongling area and the metallogenic belt of the middle-lower Yangtze. Controlling of the deep tectonosphere over the shallow-seated tectonosphere involves various grades of tectonic layering motions. Multi-layer, multi-grade, and multi-directional gliding tectonics are the specific modes of tectonic layering motions in the cover of the Tongling metallogenic cluster. The gliding tectonics developed based on S-shaped folds of the Indosinian, and was continuously active in the Yanshanian. They correspond to the deformation systems of the EW and NNE extensions. The control of tectonic layering motion acts against ore-forming processes, the different interlayer gliding belts can easily form different genetic-type deposits, and the ore-forming features of different parts of the same gliding layer are different. All of these characters are closely related to tectonic gliding mechanisms, tectonic compounding characteristics, features of metallogenic wall rocks, and types of ore-forming hydrothermal solutions.

The Formation of the Jiaodong Gold Province

Gold deposits in Jiaodong,termed Jiaodong-type,are tectonically located in the southeastern margin of the North China Craton.Their major features are reviewed in this paper to highlight the differences between Jiaodong deposits and other genetic types of gold deposits.The mineralization was synchronized with asthenosphere upwelling indicated by synore OIB-like mafic dike and large-scale crustal thinning suggested by decrease of Sr/Y from pre-ore to syn-ore granites.Asthenosphere upwelling induced by the roll-back of Paleo-Pacific Plate drove partial melting of lithospheric mantle and devolatilization,which induced the release of the ore-forming fluids.In concomitant with magmatic records,mineralization migrated from the western Jiaobei terrane(133–127 Ma)to the eastern Sulu orogenic belt(114–108 Ma),corresponding to the eastward roll-back of Paleo-Pacific Plate.Gold mineralization in Jiaodong formed in the transitions of ductile to brittle deformation,rapid to slow crustal uplift,and regional compression to extension.In the regional-scale,the gold deposits in the Jiaobei terrane are mostly situated at intersections between NE-trending faults and EW-trending basement faults,and gold orebodies dominantly controlled by the lithologic contacts between Precambrian metamorphic rocks and Mesozoic granites.The mineralization was dominated by the disseminated-veinlet ores related to quartz–sericite alteration in strong cataclasite-breccia zone,with subsidiary thick quartz-sulfide veins developed in secondary fault zones.The ore-forming fluids belong to a H_(2)O–CO_(2)–NaCl±CH_(4)system and show minor variations in salinity among different types of ore.Structure-fluid feedback involving fluid-rock reaction and hydrofracturing triggered the fluid phase separation and resultant gold deposition.The Jiaodong gold deposits are distinct from orogenic and intrusion-related gold deposits in terms of tectonic setting,origin of ore-forming fluids,and mechanism of gold deposition.

Ore-forming fluid and mineralization of Caijiaying and Dajing polymetallic ore deposits

Fluid inclusions from the Dajing and Caijiaying deposits have nearly the same homogenization temperature. Correlation between temperature and salinity shows that both Sn- and Cu-bearing fluids Sn and Cu were present in the Dajing deposit but only one kind of fluids continuously evolved in the Caijiaying deposit. Study on rare earth elements (REE) in ancient fluid from the inclusions indicates that the fluid of Sn mineralizing stage in Dajing was derived from remelting magma of the continental crust, and the fluid of Cu-Pb-Zn mineralizing stage in the Dajing deposit and the fluid of Cu-Pb-Zn mineralization in the Caijiaying deposit were derived from the mantle. It is concluded that the Cu-Pb-Zn mineralizations in the Dajing and Caijiaying deposits resulted from the identical tectono-thermal event of magma-fluids induced by Mesozoic tectonic transition and extension in the eastern part of North China Craton.

On deposits controlled by tectonic lenses

By study of the typical tectonic lenses controlling some ore deposits, the tectonic lens boundaries may be classified into fuzzy boundaries, sharp boundaries and complex boundaries, and the metallostructures in tectonic lenses may be classified into vein-type, stock- work-type and breccia-type. After studying their metallostructures, we suggest the conception on tectonic lenses as an ore-forming system, realizing that the compact-function ore-forming system is made up of the lenticular weak-strain domain(Q) and its outside linear strong-strain belt(P). The ore-forming system, which is composed of four subsystems that coupled with each other and exert their system functions to the full, includes the dual-dynamical system made up of tectonic and fluid dynamics, the metallotectonic system controlled by hydrofracturing, the ore-source system made up of multi-substances and the mineral transportation system contacted by tectonic network. Deformational partitioning, hydrofracturing and tectonic pumping operate the consid- erable function while the system function practises. Finally, the significance of metallotectonics on the tectonic lenses is discussed in the paper.

ON SOME KEY GEOLOGICAL PROBLEMS RELATED TO THE LINGLONG-JIAOJIA ORE-CENTRALIZED DISTRICT IN SHANDONG PROVINCE,CHINA

The Linglong-Jiaojia ore-centralized district is controlled by the tectonic stress field characterized by the combination of extension and strike-slip, and the dip, dip angle, pitch and pitch angle of the ore bodies are all constrained by the dynamic conditions of the tectonics. The metallotectonic series for the ore-centralized district belong to the type of a combination of extension and strike-slip and can be subdivided into four sub-series. The ore-forming process in the brittle regime can be disintegrated into two stages, i.e., the embryonic fracture stage and the megascopic fracture stage, and ore-forming process is rather common in the ore-centralized district at the former stage. Moreover, several key structural patterns and their features were discussed and a preliminary assessment about the ore-forming prospect in this district was made in the paper.

Large clusters of gold deposits and large-scale metallogenesis in the Jiaodong Peninsula, Eastern China

The Jiaodong Peninsula is the largest repository of gold in China based on the production in history. It covers less than 0.2% of China's territory, but production of gold accounts for about one fourth of the whole country. Thus, the Jiaodong Peninsula is a typical area or case of large-scale metallogenesis and a large clusters of mineral deposits in China. It is characterized by the large clusters of gold deposits in large scale, high reserve and short mineralizing stage. In this study, we suggest that the eastern boundary of the large clusters of gold deposits is as same as that of North China Block, the gold deposits are hosted by Archean metamorphic rocks or Mesozoic granites, and the age of gold mineralization is 121.6 to 122.7 Ma. Gold and related ore-forming materials are derived from multisources, i.e. Archean metamorphic rocks, granites and intermediate-mafic dikes, especially, intermediate-mafic dikes and calc-alkaline granites. The metallogenic geodynamic process is constrained by the tectonic evolution of eastern North China Block during Late Mesozoic, and it is the result of the interaction between mantle and crust as the boundary plates are playing role on the block.