Metallogenic Processes:Evidencesfrom Zoning Patterns of Mineralization and alteration and fluid inclusion geochemistryin the Lehong Zn-Pb Deposit in Northeastern Yunnan, China

1 Introduction The large clusters of Zn-Pb deposits in northeastern Yunnan,located in the southwestern margin of the Yangtze Block,are an important part of the Sichuan-YunnanGuizhou Pb-Zn Poly-metallic Metallogenic Triangle Area

Mineral Geochemical Compositions of Tourmalines and Their Significance in the Gejiu Tin Polymetallic Deposits, Yunnan, China

The Gejiu tin polymetallic deposits are located in the southeastern part of Yunnan Province in China. A detailed electronic microprobe study has been carried out to document geochemical compositions of tourmalines from the deposits. The results indicate a systematic change of mineral geochemical compositions, which might be used as a mineral geochemical tracer for post-magmatic hydrothermal fluid, basin fluid and their mixture. The tourmalines from granite are schori with Fe/ （Fe＋Mg） ratios of 0.912-1.00 and Na/（Na＋Ca） ratios of 0.892-0.981. Tourmalines as an inclusion in quartz from the ore bodies are dravite with Fe/（Fe＋Mg） ratios of 0.212-0.519 and Na/（Na＋Ca） ratios of 0.786--0.997. Tourmalines from the country rocks are dravite with Fe/（Fe＋Mg） ratios of 0.313--0.337 and Na/（Na＋Ca） ratio of 0.599-0.723. Tourmalines from cassiterite-tourmaline veins that occur in crannies within the country rocks show distinct optical zoning with alternate occurrence of dravite and schorl, Fe/（Fe＋Mg）=0.374-0.843, Na/（Na＋Ca）=0.538-0.987. It suggests that schorl in granite and dravite in carbonatite are related to magmatic fluid and basin fluid respectively. When magmatic fluid rose up and entered into crannies of the country rocks, consisting mainly of carbonatite, basin fluid would be constantly added to the magmatic fluid. The two types of fluid were mixed in structural crannies of the sedimentary basin accompanied with periodic geochemical oscillations to form material records in chemical composition zonings of tourmalines.

Effects of grain size on landscape patterns in mineral resource zones:a case study of Wu’an,China

A mineral resource zone,rich in resources and energy,is intensively developed and disturbed by human activities,which causes an obvious change of landscapes.Taking Wu’an of Hebei Province,China,as a case study,this paper extracts landscape information of mineral resource zones through overlapping mineral resources distribution map and landscape pattern map.And then,various landscape indices are selected for analyzing the effects of grain size(30,60,90,120,150,180,210,240,270 and 300 m)on landscape patterns.Due to different kinds of landscape information transmitted by indices,the changing trends vary with the increase of grain sizes.Accordingly the landscape indices are classified into three types of effects:disturbance,continuity and sustainability,and each type of effect has its own optimal range for grain sizes.Then the optimal range of grain size on landscape patterns in mineral resource zones is gained through a comparison of the effects in various grain sizes of landscape indices.The best first domain of scale covers 30-90 m,with a suitable grain size of 30-60 m before intensive mining and a suitable grain size of 60-90 m after intensive mining.Besides,the suitable grain sizes for reflecting disturbance,continuity and sustainability before intensive mining are 30-60,30-60 and 30-90 m,respectively,however,the sizes are changed to 60-90,60-90 and 30-90 m,respectively,after intensive mining.The results are helpful for rational land use and optimal landscape allocation.

South-Altai Mineralization Zone

Altai mineralization zone is located in the north-west of Xinjiang Uigur Autonomous Region.Throughout the zone 70 and more mineral species have been discovered.There are 46 mineral spe-cies reserve of which hag been verified.Altai is an importantest place of occurrence of beryllium,lithium,tantalum,niobium and other rare metals.It is also a producing area of high-qualitymuscovite,biotite and other mica.The precious stone,lade and marble are also produced there.

Preliminary Study of the Characteristics and Genesis of Arsenate Minerals in the Oxidized Zone of the Debao Skarn-Type Cu-Sn Ore Deposit in Guangxi

Through the study of the oxidized zone of the Debao skarn-type Cu-Sn deposit in Guangxi, the authorshave found 14 arsenate minerals, most of which are for the first time reported in China. They are mainly Cuarsenate minerals with subordinate Cu-Pb arsenate minerals and minor Fe-Pb-Ba varieties. Based on their paragenesis these minerals may be divided into the following series: (1) the clinoclasite-olivenite-cornwallite- cornubite- debaoite- copper silicarsenate association, (2) the scorodite- carminite- beudan-tite-bayldonite- duftite association, and (3) the scorodite-Ba-bearing pharmacosiderite- dussertite association. Arsenate minerals are formed generally in the oxidized zone of the sulfide-type deposits which lie in thewarm, humid and rainy torrid-subtropical zone with pH=6-8 and contain large amounts of arsenopyrite andcarbonate rocks.

Isotopic Ages of the Carbonatitic Volcanic Rocks in the Kunyang Rift Zone in Central Yunnan,China

The Mesoproterozoic Kunyang rift, which is located on the western margin of the Yangtze platform and the southern section of the Kangdian axis, is a rare massive Precambrian iron-copper polymetallic mineralization zone in China. The Mesoproterozoic Wulu (Wuding-Lufeng) basin in the middle of the rift is an elliptic basin controlled by a ring fracture system. Moreover, volcanic activities in the basin display zonation of an outer ring, a middle ring and an inner ring with carbonatitic volcanic rocks and sub-volcanic dykes discovered in the outer and middle rings. The Sm-Nd isochron ages have been determined for the outer-ring carbonatitic lavas (1685 Ma) and basaltic porphyrite of the radiating dyke swarm (1645 Ma) and the Rb-Sr isochron ages for the out-ring carbonatitic lavas (893 Ma) and the middle-ring dykes (1048 Ma). In combination of the U-Pb concordant ages of zircon (1743 Ma) in trachy-andesite of the corresponding period and stratum (1569 Ma) of the Etouchang Formation, as well as the Rb-Sr isochron age (1024 Ma) and K-Ar age (1186 Ma) of the dykes in the middle ring, the age of carbonarites in the basin is preliminarily determined. It is ensured that all of these carbonatites were formed in the Mesoprotero/oic period, whereby two stages could be identified as follows: in the first stage, carbonatitic volcanic groups, such as lavas, pyroclastic rocks and volcaniclastic sedimentary rocks, were formed in the outer ring; in the second stage, carbonatitic breccias and dykes appeared in the middle ring. The metamorphic age of the carbonatitic lavas in the outer ring was determined to be concurrent with the end of the first stage of the Neoproterozoic period, corresponding to the Jinning movement in central Yunnan.

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.