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Yangshan Superlarge Gold Deposit Geology And Geochemistry Characteristic And Ore Deposit Origin In Wenxian County, Gansu Province

Posted on:2008-07-01Degree:MasterType:Thesis
Country:ChinaCandidate:C W ZhangFull Text:PDF
GTID:2120360215965013Subject:Mineralogy, petrology, ore deposits
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Yangshan gold deposit located in the northwest trigile gold belt which tie three provinces of Shanxi, Gansu and Sichuan, is the largest fine-grained disseminated gold deposit currently. This article studies indicated, Yangshan gold deposit not only has the classical characteristic of Carlin type gold deposit, moreover, this superlarge gold deposit has recorded the complexity of mineralization and the geological haracteristic which the common gold deposit does not have, in particular ore-body of carlin and carlin-like compound type gold deposit coexistence and transition. The development to this ore deposit research, and consummates the understanding to the scientific research to have the important theory significance. has the important practical significance to the exploration development as well as the economical development.The research yields the following result and knew that, The Yangshan gold deposit, located in the particular geotectonic position of convergent transform of Yangtze craton, Sino Korean craton and Song pan plot, also the growth contains the ore good sedimentary formation, the special structure background and the advantageous sedimentary formation are advantageous to the mineralization. The auric rock is a suit of auric carbon-silicon-mud stratum of Devonian, which contains abundant strawberry pyrite with unusual As, and muddy oolite has been found in the thin alternation of powdery sand shale and quartziferous powdery sandstone. Tenacity-brickie shearing structure sequence develops very well, and the Plagiogranite body intruded along stratum. Orebodies distribute along the fault belt equidistantly like a string of beads, they are produced in the secondary cracked belt or shearing belt along the stratum. Au presents with ulmicrostucture and sightless state in pyrite and arsenopyrite containing unusual As. Pyrite with unusual as develop hyperplastic zone-inner lower as zone and outer higher as zone. The minerals carrying Au distribute along the slice belt with micro-dissemination state.The geochemistry research indicated that, Yangshan gold deposit formation is relevant to the mineralization fluid activity ,which richly contains low temperature hydrothermal element for example of the Au, As, Sb, Bi, Hg and so on. The fluid activity has the tendency to the depth portion which weakens. The ore deposit ore forming element combination is Au-Ag-As-Hg-Sb-Ba-Te-Cu-Pb-Zn-Bi. The∑REE of Plagiogranite is 82.41ppm, the LREE enrich and Eu waned obviously .The curve of Chondrite- normalized diagram leans to right with V mode, so the Plagiogranite came from remelting lithosphere, and the Plagiogranite types indicate the magma had intruded many times. Fluid inclusions in quartz have homogenization temperatures from 105℃to 310℃,salinity ranges from 1.6 to 10.4 NaCl equivalent wt percent,demonstrates the hydrothermal deposit characteristic. The sulfur isotope (δ34 S values of mining area rock and ore range from -29.0‰to 13.23‰) composition and characteristic to indicate the sulfur was the many kinds of origins mix, stratum S, biological S and rock magma S participated in the mineralization. The oxyhydrogen isotope (δD values of fluid inclusions in quartz from 92.4‰to 60.0‰,δ18O values of quartz from-3.23‰to 22.7‰) composition and characteristic to indicate the mineralization fluid originates by the atmospheric precipitation primarily, and has the juvenile water participation.This article evolves to the ore deposit mineralization from the ore rock is mineralizes the matter to concentrate, the structure transformation function, the rock magma hydrothermal superimposition function, the surface oxidation these four aspects in advance elaborates.Structure transformation function divides into the early time ductile sheer, the intermediate stage of brickie-ductile sheer and the later period brickie structure three stages. This article divides the ore deposit mineralization time for the period of the matter to concentrate ,the period of rock magma-structure-hydrothermal transformation and the period of surface oxidation. The period of Rock magma-structure-hydrothermal mineralization might has divided six mineralization stages according to the mineral characteristic and the combination. The Yangshan gold ore deposit displays the classical Carlin type gold ore characteristic includes: The mineralization geochemistry element combination has include stricted the element of Au-As-Hg-Sb and so on. the arsenic-rich pyrite contains gold distribute as-rich rims, when arsenic replacement sulfur of the metal sulfides ,the causes in the crystal lattice to have the fault of construction, and causes gold save in the arsenian sulfide as the form of submicrometer-size gold. This ore deposit displays the Carlin-like type gold ore deposit characteristic includes: the granite invasion ore rock and assumes the structure lens directly to participation controls the ore in the tough shear zone.In the tough shear zone the granitoid intrusion occur the mild intermediate stage pyrite- arsenopyrite - silkmica. Because mineralizes is fully there reveals visible native gold in the midterm and later period quartz. The ore deposit Carlin type characteristic mainly appears the early-midterm stage and the stibnite stage which distorts in the mineralization morning-intermediate stage as well as brittleness, the Carlin-like type characteristic mainly appears in the mineralization midterm-later period stage.In summary, the Yangshan gold deposit is the specific stratum -lithological character, the structure control and has with the magmatic activity the golden ore deposit which the origin relates. There deposited a suit of rich auric carbon-silicon-mud stratum of Devonian , the thin interbed rhythm extremely grew, just -modelled the lithological character to alternate with, advantageous later period crisp - tough shear structure full transformation. Adds the early period magmatic activity, with enough contains the ore hydrothermal safeguard, enable in the construction the gold to obtain the full activation, the migration, finally expands in the advantageous mineralization allows the structure spot precipitation to concentrate, approximately experienced the deposition to concentrate the structure superimposition transformation-agmatic activity superimposition mineralization process in advance. All above indicated Yangshan gold deposit is directly cont rolled by Devonian sediment, magmatic activities and tectonic-hot liquid alteration. It is a superlarge carlin and carlin-like multiple type gold deposit.
Keywords/Search Tags:yangshan gold deposit, ore deposit geology and geochemistry characteristic, mineralization evolution, ore deposit origin, controlling factors of deposit, carlin and carlin-like multiple type gold deposit
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