Anoxic environment and formation of superlarge ore deposits

The formation of many metallic and non-metallic ore deposits is a result of coupling of mineralization, related to anoxic environment and regional, or global background. Inter act~on, concordance and continual development of the mineralization and environmental background control the large to superlarge scale of ore deposits. Three kinds of ore-forming models related to anoxic environment and three important background patterns are suggested. The turning period of geological history is favorable to the formation of large to superlarge ore deposits.     

Bio-reef-chert suite and superlarge ore deposits

The bio-reef-chert suite is an important ore-bearing rock assemblage and one of the metallogenic rock suites of superlarge ore deposits. It is formed as a fixed and ordered suite in space and time, and composed of different rocks formed by different geological processes. It is the product of basin evolution at special stage in a special geological setting. It is also the comprehensive product of normal sedimentary process, biological process in basin, hydrothermal sedimentary process under basin base and magmatic process in the deep lithosphere.     

Synchronous structure control of superlarge ore deposits

The control of synchronous structures on formation of superlarge stratabound ore deposits is immense. Based on studies of ore deposits in South Qiniing, northern Guangdong, Langshan and other areas, three new ideas in comparison with examples of ore control of synchronous structures both in China and abroad are proposed: (i) multiorder ore control of synchronous structures, which means that synchronous structures of different orders display different controls on ore deposits; (ii) synchronous structures in different stages of basin evolution display different controls on basin fluid system and ore-forming system; (iii) synchronous strurture accompanying hydrothermal mineralization as a preexisting weak surface in earth crust often reactivate in later tcctono-thermal event to be a channelway for magma or thermal fluids which superimposed on and reformed preexisting ore beds to form large or superlarge composite ore deposits.     

Sea-level changes and hydrothermal sedimentary mineralization of large-superlarge ore deposits among Sinian to Triassic in South China

Among the Sinian to Triassic strata in South China, the stratiform, quasi-stratiform and lenticular metallic deposits in association with hydrothermal sedimentation mainly occur in the four periods: (1) the Sinian Datangpo interglacial period, (2) the early period of Early Cambrian, (3) the late period of Middle Devonian to early period of Late Devonian,and (4) the late period of Early Permian. The four mineralization periods all happened around the maximum flooding period in the third-order seal-level cycle during the ascending stage in the first-order sea-level cycle. The deep seawater layer, starved and non-compensatory basin, low sedimentary rate, and low energy and anoxic environment during the maximum flooding period are very suitable for the formation and preservation of large to superlarge hydrothermal sedimentary deposits. The maximum flooding period also coincided with the intensified regional tectonism, extensive deep magmatism and hydrothermal sedimentation, which provide, for the formation of large to superlarge hydrothermal sedimentary deposits through the rapid accumulation of hydrothermal sediments, the needed dynamics, ore-forming materials and favorable passway for hydrothermal fluids to enter the basin.     

Sea-level changes and hydrothermal sedimentary mineralization of large-superlarge ore deposits among Sinian to Triassic in South China

Among the Sinian to Triassic strata in South China, the stratiform, quasi-stratiform and lenticular metallic deposits in association with hydrothermal sedimentation mainly occur in the four periods: (1) the Sinian Datangpo interglacial period, (2) the early period of Early Cambrian, (3) the late period of Middle Devonian to early period of Late Devonian, and (4) the late period of Early Permian. The four mineralization periods all happened around the maximum flooding period in the third-order seal-level cycle during the ascending stage in the first-order sea-level cycle. The deep seawater layer, starved and non-compensatory basin, low sedimentary rate, and low energy and anoxic environment during the maximum flooding period are very suitable for the formation and preservation of large to superlarge hydrothermal sedimentary deposits. The maximum flooding period also coincided with the intensified regional tectonism, extensive deep magmatism and hydrothermal sedimentation, which provide, for the formation of large to superlarge hydrothermal sedimentary deposits through the rapid accumulation of hydrothermal sediments, the needed dynamics, ore-forming materials and favorable passway for hydrothermal fluids to enter the basin.     

大型超大型金属矿床综合信息成矿预测方法研究

大型超大型矿床在其时空分布、控矿因素、形成机制、成矿模式诸方面与一般中小型矿床有相似甚至雷同之处,也有其特殊、独特方面,研究预测大型超大型矿床相当复杂,需要从不同学科、不同侧面、不同角度、不同途径、不同方法及不同思路进行综合研究。本文给出大型超大型矿床预测的综合信息方法,认为地质地球物理地球化学多学科综合分析是今后找矿的最主要途径。通过对大型、超大型矿床的趋群性特点分析,给出了矿床密集区的概念以及圈定的基本原则和边界条件。通过对大型超大型矿床发现途径的分析,指出大型超大型矿床的分布具有可预测性。并表述了综合信息预测方法流程,以矿床密集区为模型单元,以异常密集区为预测单元,通过地质、地球物理、地球化学等综合信息控矿地质变量的提取和合理赋值,加上数理统计方法的合理应用,达到对大型超大型矿床的预测目的。     

Metallogenic focus-area and superlarge mineral deposits in the bordering zones between China,Russia and Mongolia

A correlative study of geology and metallogenic process in the bordering zones between China, Russia and Mongolia shows that the region of the western slope of the Da Hingan Mts. -Eastern Transbaikalia-Eastern Mongolia is a metallogenic focus-area associated with Late Mesozoic intraplate tectono-magmatic activation. During the period of 160–120 Ma a great number of multiplex deposits with similar genesis including large and superlarge mineral deposits were formed.

     

冈底斯成矿带东段的电性结构特征研究

冈底斯成矿带为我国著名的成矿区域,其东段存在一系列规模较大的矿床.为了研究冈底斯成矿带东段的电性结构特征,对覆盖主要矿集区的大地电磁测深数据进行全面的处理分析,通过二维与三维反演的综合对比得到了可靠的电性结构模型.结合其他地质与地球物理资料,对电性结构模型进行分析得到冈底斯成矿带东段的矿床分布规律:矿床主要分布在地壳浅表的电性分界面附近;中地壳高导体可能通过上地壳隐伏的南-北向断裂控制着与地壳伸展作用有关的矿床;南-北向张性构造与东-西向逆冲-推覆构造的交汇部位可能是冈底斯成矿带东段重要的成矿区域;下地壳可能受到软流圈物质上涌的影响发生部分熔融,从而与中地壳的高导体共同影响地壳浅部的成矿作用.     

A preliminary study on ore-forming environments of Xianglushan-type iron deposit and the weathering mineralization of Emeishan basalt in Guizhou Province,China

Xianglushan-type iron deposits are one of the new types of iron deposits found in the Weining Area of Western Guizhou. The iron-bearing rock system is a paleo-weathered crustal sedimentary(or accumulating) stratum between the top of the Middle-Late Permian Emeishan basalt formation and the Late Permian Xuanwei formation. Iron ore is hosted in the Lower-Middle part of the rock system. In terms of the genesis of mineral deposit, this type of deposit should be a basalt paleo-weathering crustal redeposit type, very different from marine sedimentary iron deposits or continental weathering crust iron deposits. Based on field work and the analytical results of XRD Powder Diffraction, Electron Probe, Scanner Electron Microscope, etc., the geological setting of the ore-forming processes and the deposit features are illustrated in this paper. The ore-forming environment of the deposit and the Emeishan basalt weathering mineralization are also discussed in order to enhance the knowledge of the universality and diversity of mineralization of the Emeishan Large Igneous Province(ELIP), which may be a considerable reference to further research for ELIP metallogenic theories, and geological research for iron deposits in the paleo-weathering crust areas of the Emeishan basalt,Southwestern, China.     

On the ore-forming conditions and ore-forming model of the superlarge multimetal deposit in Shizhuyuan

Eight favorable ore-forming conditions for the Shizhuyuan W-multimetal deposit are proposed. They are: (i) the geochemistry background special enriching the volatile and W and Sn ore-forming elements; (ii) the existence of melt-fluid system very rich in volatile and ore-forming elements; (iii) supply of sufficient ore-forming material and volatile multi-source; (iv) the infiltration and convection water source and driving force partly supplied by the Jurassic reservoir basin; (v) favorable tectonic conditions; (vi) ore-bearing greisen and vein superimposed in the pre-existing skarn rocks; (vii) favorable ore-transport and ore-concentration strata condition; (viii) there were a set of favorable ore-forming structures in Shizuyuan area; (ix) the orebody has good ore-reserve condition. Finally, ore-forming models are proposed. The paper is one of the achievements on the research related to the Climbing Project “The basic related to searching for the superlarge deposits supported by the State Science and Technology Commission. This research is also granted by the National Natural Science Foundation of China (Grant No. 49572134).     

闽西南多金属成矿带地质地球物理特征综合研究——以永定大排多金属矿区为例

闽西南地区位于福建武夷山成矿带西南部,自远古宙以来经历了多期次的构造演化.该区地处东南沿海构造-岩浆-成矿带上,为环太平洋大陆边缘多金属成矿带与南岭多金属成矿带复合部位,是我国重要的多金属矿产地.永定大排多金属矿区作为近年来武夷山成矿带新发现的大型多金属矿,区内叠加作用和控矿作用相对复杂,现有的地质地球物理工作程度不足以满足对该区域成矿规律的深入认识,一些基础地质问题亟待解决.因此,本文在深入收集永定大排矿区地质地球物理资料基础上,综合分析区域成矿背景与成矿构造,在重点区域布设综合地球物理勘探工作,包括1：1万高精度磁测、可控源音频大地电磁剖面及反射地震剖面.基于上述工作：1）开展了研究区航磁数据三维磁化率反演与分布特征分析与大地电磁二维电阻率反演与分布特征分析,开展了地震资料真地表深度偏移成像,获得了更加准确的地震剖面成像结果.2）结合推覆体控矿特征,地震剖面和电阻率剖面、航磁反演结果相互验证和约束,勾画了地下构造形态.地表地质剖面延伸和标定了构造形态的地质内涵,获得了从地表到3000 m深度的构造解释结果.解释结果清晰地显示了与推覆相关的构造、控矿层位以及岩体信息,为三位一体的找矿思路提供了地球物理依据.     

Alkali-rich igneous rocks and related Au and Cu large and superlarge deposits in China

The alkali-rich igneous rocks in China occur as fifteen linear distributed belts of each extending several hundreds to several thousands kilometers in length. These include most types of alkali-rich igneous rock categories discovered worldwide. The related Au, Cu large and superlarge deposits or metallogenic focus-areas include Dongping, Guilaizhuang, Yulong, etc. Direct and indirect genetic links have been found between alkali-rich igneous rocks and Au, Cu mineralization. The petrogenesis and metallogenesis of the alkali-rich igneous rocks are mainly controlled by (1) mantle enrichment, (2) strong interaction between mantle and crust, (3) lower contens of sulfur, high and high contents of volatiles, (4) the significant turn of regional tectonic framework from compress to extension and (5) the strong change of regional lithosphere structure.     

Alkali-rich igneous rocks and related Au and Cu large and superlarge deposits in China

The alkali-rich igneous rocks in China occur as fifteen linear distributed belts of each extending several hundreds to several thousands kilometers in length. These include most types of alkali-rich igneous rock categories discovered worldwide. The related Au, Cu large and superlarge deposits or metallogenic focus-areas include Dongping, Guilaizhuang, Yulong, etc. Direct and indirect genetic links have been found between alkali-rich igneous rocks and Au, Cu mineralization. The petrogenesis and metallogenesis of the alkali-rich igneous rocks are mainly controlled by (1) mantle enrichment, (2) strong interaction between mantle and crust, (3) lower contens of sulfur, high f _O2 and high contents of volatiles, (4) the significant turn of regional tectonic framework from compress to extension and (5) the strong change of regional lithosphere structure.     

Analysis of tectonic settings of global superlarge porphyry copper deposits

About three quarters of superlarge porphyry copper deposits throughout the world occur along the eastern Pacific basin rim, most of which were formed during the Mesozoic-Cenozoic. Porphyry copper deposits often occur in the upper parts of a subduction zone and in a within-plate orogenic belt. Some porphyry copper deposits are inconsistent with plate subduction with respect to their formation time, and most of them in the world are associated with tensional environment. Metallogenic porphyries originated from the mantle, and the involvement of the lower-crust or oceanic crust materials have played an important role. Based on the geochemical characteristics and tectonic settings of the ore-bearing porphyries in the Gandise and Yulong metallogenic zones, it is proposed that delamination may be the important mechanism of formation of porphyry copper deposits.     

江西武夷成矿带铜多金属矿产资源远景评价与展望

华南武夷山地区处于扬子、华夏两大构造单元交接叠加地段,构造变形复杂,中生代岩浆活动强烈,具有十分优越的成矿条件,矿产资源潜力巨大。本文以正在武夷山成矿带开展的矿产远景调查工作和资源评价工作所取得的阶段性成果为基础,分析了武夷山成矿带的成矿地质背景、主要矿床类型及近几年的找矿勘查成果,并对武夷成矿带江西省境内铜多金属矿产资源潜力进行了初步评价,划分了十七个找矿远景区。     

Analysis of tectonic settings of global superlarge porphyry copper deposits

About three quarters of superlarge porphyry copper deposits throughout the world occur along the eastern Pacific basin rim, most of which were formed during the Mesozoic-Cenozoic. Porphyry copper deposits often occur in the upper parts of a subduction zone and in a within-plate orogenic belt. Some porphyry copper deposits are inconsistent with plate subduction with respect to their formation time, and most of them in the world are associated with tensional environment. Metallogenic porphyries originated from the mantle, and the involvement of the lower-crust or oceanic crust materials have played an important role. Based on the geochemical characteristics and tectonic settings of the ore-bearing porphyries in the Gandise and Yulong metallogenic zones, it is proposed that delamination may be the important mechanism of formation of porphyry copper deposits.     

The characteristics,origins, and geodynamic settings of supergiant gold metallogenic provinces

There are six distinct classes of gold deposits, each represented by metallogenic provinces, having 100's to >1000 tonne gold production. The deposit classes are: (1) orogenic gold; (2) Carlin and Carlin-like gold deposits; (3) epithermal gold-silver deposits; (4) copper-gold porphyry deposits; (5) iron-oxide copper-gold deposits; and (6) gold-rich volcanic hosted massive sulfide (VMS) to sedimentary exhalative (SEDEX) deposits. This classification is based on ore and alteration mineral assemblages; ore and alteration metal budgets; ore fluid pressure(s) and compositions; crustal depth or depth ranges of formation; relationship to structures and/or magmatic intrusions at a variety of scales; and relationship to the P-T-t evolution of the host terrane. These classes reflect distinct geodynamic settings. Orogenic gold deposits are generated at mid-crustal (4–16 km) levels proximal to terrane boundaries, in transpressional subduction-accretion complexes of Cordilleran style orogenic belts; other orogenic gold provinces form inboard, by delamination of mantle lithosphere, or plume impingement. Carlin and Carlin-like gold deposits develop at shallow crustal levels (<4 km) in extensional convergent margin continental arcs or back arcs; some provinces may involve asthenosphere plume impingement on the base of the lithosphere. Epithermal gold and copper-gold porphyry deposits are sited at shallow crustal levels in continental margin or intraoceanic arcs. Iron oxide copper-gold deposits form at mid to shallow crustal levels; they are associated with extensional intracratonic anorogenic magmatism. Proterozoic examples are sited at the transition from thick refractory Archean mantle lithosphere to thinner Proterozoic mantle lithosphere. Gold-rich VMS deposits are hydrothermal accumulations on or near the seafloor in continental or intraoceanic back arcs.

The compressional tectonics of orogenic gold deposits is generated by terrane accretion; high heat flow stems from crustal thickening, delamination of overthickened mantle lithosphere inducing advection of hot asthenosphere, or asthenosphere plume impingement. Ore fluids advect at lithostatic pressures. The extensional settings of Carlin, epithermal, and copper-gold porphyry deposits result from slab rollback driven by negative buoyancy of the subducting plate, and associated induced convection in asthenosphere below the over-riding lithospheric plate. Extension thins the lithosphere, advecting asthenosphere heat, promotes advection of mantle lithosphere and crustal magmas to shallow crustal levels, and enhances hydraulic conductivity. Siting of some copper-gold porphyry deposits is controlled by arc parallel or orthogonal structures that in turn reflect deflections or windows in the slab. Ore fluids in Carlin and epithermal deposits were at near hydrostatic pressures, with unconstrained magmatic fluid input, whereas ore fluids generating porphyry copper-gold deposits were initially magmatic and lithostatic, evolving to hydrostatic pressures. Fertilization of previously depleted sub-arc mantle lithosphere by fluids or melts from the subducting plate, or incompatible element enriched asthenosphere plumes, is likely a factor in generation of these gold deposits. Iron oxide copper-gold deposits involve prior fertilization of Archean mantle lithosphere by incompatible element enriched asthenospheric plume liquids, and subsequent intracontinental anorogenic magmatism driven by decompressional extension from far-field plate forces. Halogen rich mantle lithosphere and crustal magmas likely are the causative intrusions for the deposits, with a deep crustal proximal to shallow crustal distal association. Gold-rich VMS deposits develop in extensional geodynamic settings, where thinned lithosphere extension drives high heat flow and enhanced hydraulic conductivity, as for epithermal deposits. Ore fluids induced hydrostatic convection of modified seawater, with unconstrained magmatic input. Some gold-rich VMS deposits with an epithermal metal budget may be submarine counterparts of terrestrial epithermal gold deposits. Real time analogs for all of these gold deposit classes are known in the geodynamic settings described, excepting iron oxide copper-gold deposits.

     

Isotopic indication to source of ore materials and fluids of the Wangfeng gold deposit in Tianshan: A case study of metallogenesis during collisional orogenesis

The Wangfeng gold deposit is one of the five most important gold deposits in the Tianshan. Studies of its metallogenic time, space, geodynamic background, ore feature and ore fluid have proved that the deposit formed in the late Paleozoic continental collision, and consequently is a suitable delegate to probe mineralizing regularities during collisional orogenesis. Isotopic studies including O, D, C, S, Pb and Sr reveal ore materials derived from sedimentary association (including carbonate and sulfate), which further refers to the Hercynian carbonate-silicolite-argillite formation north to Wangfeng camp. At the end of Paleozoic, the southward intracontinental subduction of Hercynian synthem along the Hongwuyueqiao fault down to the Central Tianshan terrane induced large-scale fluidization which extracted and out-transported ore materials from Hercynian synthem upto shallow fair positions, and finally resulted in the formation of the Wangfeng deposit. This study excludes the possibility of other tectonic metallogenic models other than the tectonic model for collisional metallogenesis, petrogenesis and fluidization.     

Metallogenesis of the Ertix gold belt, Xinjiang and its relationship to Central Asia-type orogenesis

The Ertix gold belt is located on the boundary of the Kalatongke arc and the Kelan back-arc basin of D-C1. Most scholars used to interpret the formation and distribution of the gold deposits in the Ertix tectonic belt in terms of the petrogenic and metallogenic models for active continental margins. However, enormous data of isotopic dating and geologic research show that the mineralization was obviously later than the oceanic subduction, whereas exactly simultaneous with the collisional orogenesis during C₂-P, especially at the transition stage from collisional compression to extension. Based on study of metallogenic time, tectonic background, ore geology, ore fluid nature, ore material source, etc., we reveal that all the gold deposits possess the character of orogenic deposits formed in collisional orogenic system, and that their ore-forming materials mainly have derived from the stratigraphic terranes south to individual deposits. Accordingly, the theoretical tectonic model for collisional metallogenesis and petrogenesis is employed to explain the formation of the Ertix gold belt and to determine the gold exploration directions.     

综合物探方法在好力宝铜矿床的应用

本文介绍了综合物探快速评价体系在好力宝铜矿的应用过程.通过分析地质资料和实际地质情况,综合运用VLF、EH4和IP等物探手段进行隐伏矿体预测,在工作区内发现了与成矿有关的地球物理异常,显示了良好的成矿前景.两个验证钻孔都有工业矿质发现,说明该综合物探评价体系在好力宝铜矿的应用是成功的,也显示了其快速、高效和实用的优点.