Red Clay Type Gold Deposits in China

Red clay type gold deposits,located in the south of China,are situated not only in orogenic belts,but also in inner cratons,where climate is tropical-subtropical with clear arid and humid.The lateritic weathering crust often can be divided into five zones,including topsoil,siliceous duricrust zone,multi-color zone(or red clay zone in some deposits),pallid zone and saprolite zone from surface to the base rock,several of which are absent in some deposits.The base rocks are composed mainly of carbonate rocks with minor clastic rocks,intermediate-basic volcanic rocks and intermediate-acid and alkalic intrusions.The orebodies are mainly located in the multi-color zone with part of them in the pallid and saprolite zones.The ore sources include orebodies of Carlin-type gold deposits and porphyry gold deposits,as well as gold-rich base rocks.The red clay type gold deposits experienced early-stage endogenic gold mineralization and laterization during the Tertiary and Quaternary.The areas with endogenic gold deposits,especially Carlin-type gold deposits and porphyry gold deposits in karst depressions on the plateau,structual erosional platforms in the middle-lower mountains,and intermountain basins in southern China are well worth studying to trace red clay type gold deposits.

The Bulong Gold Deposit-a Quartz-Barite Vein Type Gold Deposit in Xinjiang:Geological Characteristics and S, He and Ar Isotopic Compositions

The Bulong gold deposit, located in the southwest Tianshan in China, occurs in the Upper Devonian finegrained clastic rocks. The gold orebodies are controlled by an gently inclined interlayer fractured zone. They are hosted only in quartz-barite veins though there are barite veins and quartz veins in the ore district. The δ34S values of pyrite in the ores range from 14.6‰ to 19.2‰ and those of barite from 35.0‰ to 39.6‰, indicating that the sulfur was derived from the strata. 3He/4He ratios of fluid inclusions in pyrite are 0.24-0.82 R/Ra, approximating to that of the crust. The 40Ar/39Ar ratios range from 338 to 471, slightly higher than that of the atmosphere. 40Ar /4He ratios of ore fluids range from 0.015 to 0.412 with a mean of 0.153. Helium and argon isotope compositions of fluid inclusions show that the ore fluids of the Bulong gold deposit were mainly derived from the crust.

Locating Mechanism of Quartz Vein Gold Deposits in Rushan, Shandong Province

According to the differences in ore-controlling structural systems and the characteristics of host rocks, textures and structures of ores and mineral associations of ores, quartz vein-type gold deposits in the Rushan area can be divided into the Rushan and Tongling styles. Rushan style gold deposits, occurring in the Kunyushan complex, include Rushan, Tangjiagou and Tongxishan gold mines. They are distributed along four NNE-trending and sinistral, compresso-shear faults with a right stepping array. A prominent characteristic of the gold mineralization is that the orebodies in neighbouring gold deposits distributed in a single ore-controlling fault zone take opposite pitches. Study of the locating structures of the quartz vein gold deposits shows that the Rushan-style gold deposits are characterized by NNE and NE zoning. Therefore, the intersections of the NE direction of the known gold deposit and the neighbouring NNE-trending fault zones are favourable for looking for gold deposits, and the ends of the curving segments of sinistral and right-stepping faults are favourable for looking for large gold deposits. Tongling-style gold deposits occur in the Sanfosan porphyritic monzonitic granite. Emplacement of gold deposits is controlled by arcuate and radiate structures formed during the intrusion of the Sanfoshan porphyritic monzonitic granite; the radiate faults controlled the distribution of orebodies and the arcuate faults controlled the pitch of the orebodies.

THE GEOLOGY AND GENESIS OF THE Q1YUGOU EXPLOSIVE BRECCIA TYPE GOLD DEPOSITS,HENAN PROVINCE

The Qiyugou explosive breccia type gold deposits of northwestern Songxian, Henan Province is situated at the East Qinling, on the southern margin of the North China Platform.The basement rocks are the Archean Taihua Group gneisses which were overlaid by the Proterozoic Xionger Group metaandesites. NW-and NE-trending folds and fractures are well developed. Nlagmatism of the Mid-Late Yanshan Epoch led to the formation of the Huashan granite batholith and a variety of acid/alkali dykes, meanwhile more than thirty explosive breccia bodies had been brought about. The most important deposit type is the explosive breccia type represented by the Qiyugou deposit, meanwhile there are structure fracture altered rock type,the goldbearing quartz vein type, as well as porphyry-breccia type. All these types are the terminal products of the evolution and differentiation of the syntectic magma originated from lower crust or upper mantle. They are controlled by a unified structural pattern occurred in the same

Metallogenic Epoch of Nonferrous Metallic and Silver Deposits in the Jiaodong Peninsula, China and its Geological Significance

As China＇s most important gold-producing district, the Jiaodong Peninsula also contains copper, lead-zinc, molybdenum （tungsten）, and other nonferrous metal ore deposits, but the space-time and genetic relationships with gold deposits remain uncertain. To investigate the temporal relationship between these nonferrous metal and gold ore deposits, We collected the samples from a number of nonferrous metallic and silver deposits and metallogenetic rock bodies in the eastern Jiaodong Peninsula for isotopic dating. The results show that the Re-Os isotopic model ages of the Lengjia molybdenum deposit in Rongcheng range from 114.5 ± 1.8 Ma to 112.6 ± 1.5 Ma, with an average age of 113.6 ± 1.6 Ma; the LA-ICP-MS ^206pb/^238U ages of 33 zircons in the sericitization porphyritic monzogranite that hosts the Tongjiazhuang silver deposit in Rongcheng range between 122 Ma and 109 Ma, with a weighted mean age of 116.04 ± 0.95 Ma; the LA-ICP-MS ^206pb/^238U ages of 31 zircons in the copper metallogenic pyroxene monzodiorite that hosts the Kuangbei copper deposit in Rongcheng range from 126 Ma to 106 Ma, with a weighted mean age of 116.6 ± 1.7 Ma; and the LA-ICP-MS ^206pb/^238U ages of 19 zircons in the pyroxene monzodiorite surrounding the Dadengge gold and multimetal deposit in Weihai range from 113 Ma to 110 Ma, with a weighted mean age of 111.7 ± 0.6 Ma. All these results indicate that the metallogenic ages of the silver and nonferrous metallic deposits in the Jiaodong Peninsula are in a limited range from 118 Ma to 111 Ma. Previous studies have demonstrated that the isotopic ages of gold deposits in the Jiaodong Peninsula range from 123 Ma to 110 Ma, while Weideshanian magmatism occurred between 126 Ma to 108 Ma. Both these ranges are grossly consistent with the metallogenic ages of silver and nonferrous metallic deposits in this study, suggesting that the large-scale mineralization occurred in the Early Cretaceous when magmatic activities were strong. This epoch may be linked to the lithosphere thinning and the thermo-upwelling extension in eastern China at that time. In addition, field investigation also shows that gold and nonferrous metallic deposits are distributed nearby the Weideshanian granite, with the nonferrous metallic deposits lying within or surrounding the granite pluton and the gold deposits outside the granite pluton. We propose the following mineralization scenario： In the Early Cretaceous, an intensive lithospheric extension induced partial melting and degassing of the metasomatized lithospheric mantle, which resulted in the formation of mantle-derived fluids enriched in metal elements. During the rapid process of magma ascent and intrusion, crust-derived fluids were activated by the magmatic thermal dome and served to further extract ore-forming materials from the crust. These fluids may have mixed with the mantle-derived fluid to form a crust-mantle mixing-type ore-forming fluid. The high-temperature conditions in the center or in contact with the granitic magmatic thermal dome would have been favorable for the formation of porphyry-type, skarn-type, and hydrothermal-vein-type ores, thus forming a series of Mo（W）, Cu, and Pb-Zn deposits in the mid-eastern Jiaodong Peninsula. In contrast, the medium- to low-temperature conditions in the periphery of the magmatic thermal dome would have favored the deposition of gold （silver） ores under the appropriate physiochemical and structural conditions. The metaliogenic epoch of the molybdenum, copper, and silver deposits, and their spatio-temporal and genetic relations to the gold deposits, as demonstrated in this study, not only provide important insights to the study of regional metallogeny, our understanding of the metallogenesis of the Jiaodong type gold deposit, and the geodynamic background of the large-scale mineralization in the Jiaodong Peninsula, but also have practical value in guiding the mineral exploration.