Spatial-Temporal Distribution, Geological Characteristics and Ore-Formation Controlling Factors of Major Types of Rare Metal Mineral Deposits in China

Rare metals including Lithium(Li),Beryllium(Be),Rubidium(Rb),Cesium(Cs),Zirconium(Zr),Hafnium(Hf),Niobium(Nb),Tantalum(Ta),Tungsten(W)and Tin(Sn)are important critical mineral resources.In China,rare metal mineral deposits are spatially distributed mainly in the Altay and Southern Great Xingán Range regions in the Central Asian orogenic belt;in the Middle Qilian,South Qinling and East Qinling mountains regions in the Qilian-Qinling-Dabie orogenic belt;in the Western Sichuan and Bailongshan-Dahongliutan regions in the Kunlun-Songpan-Garze orogenic belt,and in the Northeastern Jiangxi,Northwestern Jiangxi,and Southern Hunan regions in South China.Major ore-forming epochs include Indosinian(mostly 200-240 Ma,in particular in western China)and the Yanshanian(mostly 120-160 Ma,in particular in South China).In addition,Bayan Obo,Inner Mongolia,northeastern China,with a complex formation history,hosts the largest REE and Nb deposits in China.There are six major rare metal mineral deposit types in China:Highly fractionated granite;Pegmatite;Alkaline granite;Carbonatite and alkaline rock;Volcanic;and Hydrothermal types.Two further types,namely the Leptynite type and Breccia pipe type,have recently been discovered in China,and are represented by the Yushishan Nb-Ta-(Zr-Hf-REE)and the Weilasituo Li-Rb-Sn-W-Zn-Pb deposits.Several most important controlling factors for rare metal mineral deposits are discussed,including geochemical behaviors and sources of the rare metals,highly evolved magmatic fractionation,and structural controls such as the metamorphic core complex setting,with a revised conceptual model for the latter.

Analysis of the Ore-Controlling Structure of Ductile Shear Zone Type Gold Deposit in Southern Beishan Area, Gansu, Northwest China

The ductile shear zone-type gold deposit is a kind that both the ore-forming mechanism and ore-controlling factors are closely related to the ductile shear zone and its evolution. Ductile shear zone develops in Beishan area, Gansu of Northwest China, and develops especially well in the south belt. The controls of the ductile shear zone on gold deposits are as follows. （1） The regional distribution of gold deposits （and gold spots） is controlled by the ductile shear zone. （2） The ductile-brittle shear zone is formed in the evolution process of ductile shear zone and both are only ore-bearing structures and control the shape, attitude, scale, and distribution of mineralization zones and ore-bodies. （3） Compresso-shear ductile deformation results in that the main kind of gold mineralization is altered mylonite type and the main alteralization is metasomatic. （4） Ore-bearing fracture systems are mainly P-type ones, some D-type and R-type ones, but only individual R＇-type and T-type ones. （5） Dynamic differen- tiation and dynamic metamorphic hydrothermal solution resulting from ductile deformation is one of the sources of ore-forming fluid of gold mineralization, and this is identical with that ore-forming materials are mainly from metamorphic rocks, and ore-forming fluid is mainly composed of metamorphic water, and with the fluid inclusion and geo-chemical characteristics of the deposit. （6） There is a negative correlation between the gold abundance and susceptibility anlsotropy （P） of the altered mylonlte samples from the deposit, which shows that the gold mineralization is slightly later than the structural deformation. All above further expound the ore-forming model of the ductile shear zone type of gold deposits.

Characteristics of mantle branch structure in western Shandong and its roles in minerogenesis and ore-controlling

This work deals with the characteristics of mantle branch structure in western Shandong Province, China, with respect to the distribution characteristics and ages of the regional strata, the development of ring-like and radial faults, the development of gently inclined detachment-slip structures in the axial part, mantle-source magmatic activities, regional petrology, petrochemistry and isotope geology. The study indicated that the N-W sharply plunged ductile shear zone in the region of western Shandong cuts through the mantle rocks detached from the deep-seated North China mantle sub-plume, hence leading to unloading in response to depressurization and thereafter the formation of anatexis magma. The intense and complete magmatic evolution series not only manifests a variation trend of alkalinity of magma from high to low and its intrusive depth from deep to shallow, but also reflects that the wall-rock alteration shows a general evolution trend from strong to weak. The evolution of mantle structure played an important role in controlling endo-mineralogenesis, accompanied with the rise of the country rocks. As a result, typical mantle branch structures were formed as observed in western Shandong. At the top of the mantle branch structure was developed an obvious detachment-tilt fault block, and some endogenic ores, at the same time, were uplifted onto the shallow levels.

Dynamo Speed Control and Tectonics—Modeling Earth as a Shunt Wound DC Machine

The Sun’s slow periodic flux transfer to the Earth, the low frequency of Schumann Resonance, and the fixed DC voltage of the capacitor direct us toward direct current (DC) machines for electrical modeling purposes. The Earth exhibits dual characteristics of a motor generator set by motoring the mechanical Earth around its axis, while at the same time generating energy for its spherical capacitor. It follows that electrical and mechanical output of the Earth are powered by the magnitude of the flux transfer events, the constant DC voltage supply and any potential nuclear contribution within the core. Like an induction furnace, powerful magnetic flux from the Sun partially melts the outer iron core of the Earth and magnetizes the inner solid iron core. The solid inner magnetic core acts as a rotating armature similar to a DC machine. All electrical machines experience no load and full load power loss while in operation. Speed control of large rotating DC machines is well understood and has been applied in industry for over a century. Speed can be changed either by varying the field resistance and/or the armature resistance. The characteristic of a constant speed DC machine is such that a change in field resistance will cause a compensatory change in armature resistance to maintain velocity. In the case of the earth, a decrease in armature resistance results in an increase in volume of the iron core, which may result in greater seismic and volcanic activity. Climate change may be the direct result of changes in soil and sea water resistance, which we lump together as field resistance.

Stability control of surrounding rocks for a coal roadway in a deep tectonic region

In order to effectively control the deformation and failure of surrounding rocks in a coal roadway in a deep tectonic region, the deformation and failure mechanism and stability control mechanism were studied. With such methods as numerical simulation and field testing, the distribution law of the displacement, stress and plastic zone in the surrounding rocks was analyzed. The deformation and failure mechanisms of coal roadways in deep tectonic areas were revealed: under high tectonic stress, two sides will slide along the roof or floor; while the plastic zone of the two sides will extend along the roof or floor,leading to more serious deformation and failure in the corner of two sides and the bolt supporting the corners is readily cut off by the shear force or tension force. Aimed at controlling the large slippage deformation of the two sides, serious deformation and failure in the corners of the two sides and massive bolt breakage, a ‘‘controlling and yielding coupling support'' control technology is proposed. Firstly, bolts which do not pass through the bedding plane should be used in the corners of the roadway, allowing the two sides to have some degree of sliding to achieve the purpose of ‘‘yielding'' support, and which avoid breakage of the bolts in the corner. After yielding support, bolts in the corner of the roadway and which pass through the bedding plane should be used to control the deformation and failure of the coal in the corner. ‘‘Controlling and yielding coupling support'' technology has been successfully applied in engineering practice, and the stability of deep coal roadway has been greatly improved.

Tectonomagmatic Metallogenic System of Dexing Ore Field, Jiangxi, China

ore deposits and a large number of ore occurrences cluster in Dexing ore field which is 20 km long and 12 km wide. The tectonic evolution, magmatism, as well as the metallogeny are controlled by the Northeast Jiangxi deep seated fracture belt (NJDFB). The source is believed to have been derived from the Meso-Neoproterozoic marine volcanism. The magmatic activity of Mesozoic I type granite could have provided the metal elements, thermal fluid, heat, and the space for ore forming processes. A unified geological model is proposed, which combines the tectonism, magmatism and metallogeny as the basic control of the giant metal mineralizations.

Mechanism of stepwise tectonic control on gas occurrence: A study in North China

To gain an understanding of gas occurrence, distribution is the fundamental basis for preventing gas disasters. Presently, how tectonic structures control gas occurrence remains problematic. This study proposes the theory and elucidates the mechanism of stepwise tectonic control on gas occurrence according to the characteristics of gas occurrence and the patterns of gas distribution in coal mines in North China. On the one hand, tectonic compression and shearing lead to stress concentration and thus deform the coal and reduce the coal seam permeability, further contributing to gas preservation. On the other hand, tectonic extension and rifting lead to stress release and thus improve the coal seam permeability, further contributing to gas emission. Therefore, the distribution zones of tectonic compression, ubiquitous coal deformation, and gas accumulation have been step-wisely revealed, and the coal-gas outburst proneness zones are finally identified. The proposed theory of step-wise tectonic control on gas occurrence is of practical significance for gas prediction and control.

The Mechanism of Structural Control of Ore Formation and Geochemical Characteristics in the Massive Sulfide Deposits of the Wushan Copper Ore Field,Jiangxi

The ore-controlling mechanism of the bedding fault system in the massive sulfide deposits of the Wushancopper orefield may be generalized as the control of ore deposition by optimum surface in an ore-formingstructural trap. The mechanism has three major features: (1) timing of mineralization; (2) positioning of hostformation; and (3) dependence of ore-controlling structure on properties of rocks. The 'optimum surface' is adivisional structural plane which marks obvious difference in physical, chemical and mechanical properties andis favorable for mineralization. It is also a unity of structures. lithofacies and orebodies. The structural and geochemical characteristics of the ore deposits indicate the migration trend of the ma-jor characteristic clements in the ore-controlling fault belt: elements with a small radius (Si, Fe, Mg and Al)moved towards and concentrated at the center of the belt while large-radius ones (Ca, K and Na) were remotefrom the center.

Tectonic Control of the Reykjanes Geothermal Field in the Oblique Rift of SW Iceland:From Regional to Reservoir Scales

This paper presents a multidisciplinary structural analysis of the Reykjanes Peninsula where Holocene deformation of a young oblique rift controls the geothermal processes in presence of a transform segment. The new structural map from aerial images and outcrops is correlated with selected surface and subsurface data and shows a complex pattern: NNE extensional rift structures, N-S dextral and ENE sinistral oblique-slip Riedel shears of the transform zone, and WNW and NW dextral oblique-slip faults. Shear fractures are more common, and along with the NNE fractures, they compartmentalise the crustal blocks at any scale. The fractures are within two ENE Riedel shear zones, indicating a minimum 7.5 km wide transform zone. The greatly deformed Southern Riedel Shear Zone is bounded to the north and the south by the 1972 and the 2013 earthquake swarms. This shear zone contains the geothermal field in a highly fractured block to the west of a major NW structure. Some of the deformations are: a) clockwise rotation of rift structures by the 1972 earthquake zone, inducing local compression;b) magma injection into extensional and oblique-slip shear fractures;c) reactivation of rift structures by transform zone earthquakes;d) tectonic control of reservoir boundaries by WNW and ENE shear fractures, and the distribution of surface alteration, fumaroles, CO2 flux, reservoir fluid flow and the overall shape of pressure drawdown by N-S, ENE, WNW/NW and NNE fractures. Results demonstrate the role of seismo-tectonic boundaries beyond which fault types and density change, with implications for permeability.

Tectonic Control of the Theistareykir Geothermal Field by Rift and Transform Zones in North Iceland:A Multidisciplinary Approach

This paper presents a multidisciplinary structural analysis of a 165 km2 area in the Northern Rift Zone and the Tjörnes Fracture Zone of Iceland, and unravels the tectonic control of the Theistareykir geothermal field and its surroundings. About 10729 fracture segments (faults, open fractures, joints) are identified in the upper Tertiary to Holocene igneous series. The segments were extracted from aerial images and hillshade, and then analyzed in terms of number of sets, geometry, motions, frequency, and relative age. The correlation with surface geothermal manifestations, resistivity, earthquakes, and occasional well data reveals the critical regional and local fractures at the surface, reservoir level and greater depth. The main conclusions of this study are: 1) The structural pattern consists of N-S rift-parallel extensional fractures and the Riedel shears of the transform zone striking NNE, ENE, E-W, WNW and NW, which compartmentalize together the blocks at any scale. 2) The en échelon segmentation shows strike and oblique slips on the Riedel shears, with a dextral component on the WNW and NW planes and a sinistral component on the NNE to ENE faults. 3) Fractures form under the influence of the transform mechanism and the effect of rifting becomes significant only with time. 4) The WNW dextral oblique-slip Stórihver Fault of the transform zone has a horsetail splay that extends eastwards into the geothermal field. There, this structure, along with few NW, ENE, NNE and N-S fractures, controls the alteration, alignment of fumaroles, emanating deep gases. These fractures also rupture during natural or induced earthquakes. 5) The resistivity anomalies present en échelon geometries controlled by the six fracture sets. These anomalies display clockwise and anticlockwise rotations within the upper 8 km crustal depth, but at 8 km depth, only three sets (the N-S rift structures, and the E-W and the NW Riedel shears) are present at the rift and transform plate boundaries. Results of this study are relevant to resource exploration in other complex extensional contexts where rift and transform interact.ööö

Geochemistry of intrusive rock in Dachang tin-polymetallic ore field, Guangxi, China: Implications for petrogenesis and geodynamics

The major element, trace element and rare earth element（REE） of the intrusion rock from the Dachang ore field in Guangxi, China, were analyzed. The results show that the phenocryst（about 15%） and matrix（about 85%） mainly consist of quartz, K-feldspar and plagioclase. The rock is composed of low content of Si and high content of Al2O3, low contents of Ca, Fe2O3, Na, TiO2, etc. The intrusion rock has the medium alkali content, attributing to K-rich type rock; and contains medium to low REE contents, of which light rare earth elements（LREEs） and heavy rare earth elements（HREEs） are highly fractionated, showing a weak negative Ce anomaly and a negative Eu anomaly. These rocks are enriched in LREE, and the large ion lithophytes elements（LILE） are rich in Rb, Sr, and U; the high-field-strength elements（Nb, Th, etc） are relatively depleted. The REE chondrite-normalized patterns are consistent with the overall, roughly indicating their similar characteristics, sources and evolution. The intrusion rock mainly formed during the collisional and within-plate periods.

Tectonic Fractures in Tight Gas Sandstones of the Upper Triassic Xujiahe Formation in the Western Sichuan Basin,China

The western Sichuan Basin, which is located at the front of the Longmen Mountains in the west of Sichuan Province, China, is a foreland basin formed in the Late Triassic. The Upper Triassic Xujiahe Formation is a tight gas sandstone reservoir with low porosity and ultra-low permeability, whose gas accumulation and production are controlled by well-developed fracture zones. There are mainly three types of fractures developed in the Upper Triassic tight gas sandstones, namely tectonic fractures, diagenetic fractures and overpressure-related fractures, of which high-angle tectonic fractures are the most important. The tectonic fractures can be classified into four sets, i.e., N-S-, NE-, E-W- and NW-striking fractures. In addition, there are a number of approximately horizontal shear fractures in some of the medium-grained sandstones and grit stones nearby the thrusts or slip layers. Tectonic fractures were mainly formed at the end of the Triassic, the end of the Cretaceous and the end of the Neogene-Early Pleistocene. The development degree of tectonic fractures was controlled by lithology, thickness, structure, stress and fluid pressure. Overpressure makes not only the rock shear strength decrease, but also the stress state change from compression to tension. Thus, tensional fractures can he formed in fold-thrust belts. Tectonic fractures are mainly developed along the NE- and N-S-striking structural belts, and are the important storage space and the principal flow channels in the tight gas sandstone. The porosity of fractures here is 28.4% of the gross reservoir porosity, and the permeability of fractures being two or three grades higher than that of the matrix pores. Four sets of high-angle tectonic fractures and horizontal shear fractures formed a good network system and controlled the distribution and production of gas in the tight sandstones.

Characteristics of Mesozoic-Cenozoic tectonic diagenesis in the Kuqa area of the Tarim Basin,China

Tectonic diagenesis is a common and important geological phenomenon. We can fully understand the diagenesis of compressional basins through studying tectonic diagenesis. In this paper, we presented the tectonic diagenetic characteristics in the Kuqa area of the Tarim Basin by integrated method of geological analysis and paleotectonic stress. The results showed that the Mesozoic-Cenozoic tectonic diagenesis affected sandstone compaction evolution mainly through physical mechanisms. It showed characteristics of abrupt change and nonthermal indicator (it means that sandstone compaction can not be explained by thermal diagenetic compaction alone because actual sandstone compaction was larger than thermal compaction), which were different from the thermal and fluid diagenesis. Compared with thermal diagenesis, tectonic diagenesis had a typical tectonic compaction in very short time, and many phases of tectonic deformation showed multiple abrupt changes of compaction. There are obvious differences between tectonic and thermal diagenetic compaction, leading to sandstone compaction being larger than the thermal compaction under the same thermal evolution stage in the areas where tectonic deformation happened. The stronger the tectonic deformation, the more obvious the difference. Tectonic process changed the stress distribution through changing the tectonic deformation styles, resulting in different tectonic diagenesis effects. Therefore, tectonic diagenesis of Mesozoic-Cenozoic in the Kuqa area can be divided into four types including rigid rock restraint, fault ramp, low angle fault slippage, and napping.

Kinetic Investigations on the Leaching of Niobium from a Low-Grade Niobium-Tantalum Ore by Concentrated KOH Solution

The leaching kinetics of niobium from a low-grade niobium-tantalum ore by concentrated KOH solu-tion under atmospheric pressure has been studied. Significant effects of reaction temperature, KOH concentration, stirring speed, particle size and inass ratio of alkali-to-ore on the dissolution rate of niobium were examined. The experimental data of the leaching rates and the observed effects of the relevant operating variables were well in-terpreted with a shrinking core model under diffusion control. By using the Arrhenius expression, the apparent activation energy for the dissolution of niobium was evaluated. Finally, on the base of the shrinking core model, the rate equation was established.

Tectonic Setting and Metallogenic System of North China Block Margins

The paleocontinental margins have frequent and intensive tectonic movement and various ore forming processes. According to their tectono dynamic characteristics, the paleocontinental margins can be classified into three types: the divergent, the convergent and the transformational. Each type has its specific geological geochemical processes and metallogenic system. The paper discusses the tectonic evolution and ore forming features of the North China block margins, puts forward conceptions such as complexity, variety and multi stage development of metallogenic evolution in the paleocontinental margins, and expounds five factors controlling the formation of large superlarge ore deposits in the paleocontinental margins: (1) channelway, (2) rendezvous of fluids, (3) abundance of ore source, (4) thermo dynamic anomaly, (5) long duration of structural activities.

Process control technology of low NO_x sintering based on coke pretreatment

Process control is an effective approach to reduce the NOx emission from sintering flue gas.The effects of different materials adhered on coke breeze on NOx emission characteristics and sintering performance were studied.Results showed that the coke breeze adhered with the mixture of CaO and Fe2O3 or calcium ferrite significantly lowers the NOx emission concentration and conversion ratio of fuel-N to NOx.Pretreating the coke with the mixture of lime slurry and iron ore fines helped to improve the granulation effect,and optimize the carbon distribution in granules.When the mass ratio of coke breeze,quick lime,water and iron ore fines was 2:1:1:1,the average NOx emission concentration was decreased from 220 mg/m3 to 166 mg/m3,and the conversion ratio of fuel-N was reduced from 54.2%to 40.9%.

Tectonic development of subtle faults and exploration in mature areas in Bohai Sea,East China

Based on the theory of structural analysis,the characteristics and structural patterns of subtle faults are studied using 3D seismic data of the Bohai Sea to analyze the development process and origin of the subtle faults.A method of identifying subtle faults is proposed,forming a complete system for analyzing origins of subtle faults in the Bohai Sea.The complex strike-slip fault patterns under the strike-slip and extension stress background,diverse formation rocks,and strong neotectonic movement are the reasons for the development of subtle faults.According to the tectonic origin and development location,the subtle faults in Bohai Sea can be divided into 12 types in the three categories of strike slip dominant,extension dominant and strike slip and extension composite,and the different types of subtle faults occur in different regions of the Bohai Sea.Unreasonable variation of sedimentary stratum thickness,inherited distortion or even abrupt change of stratum occurrence,zonation of plane fault combination and the variation of oil-water system in the same structure with no-lithologic change are the important signs for identifying subtle faults in Bohai Sea.The subtle faults greatly enlarge the size of the structural trap groups,and areas with dense subtle faults are often active area of hydrocarbon migration and accumulation and favorable exploration zones,which have strong control on the hydrocarbon accumulation.The identification method for subtle faults has guided the exploration in the mature areas of Bohai Sea effectively,with a number of large and medium oil and gas fields discovered,such as Bozhong 29-6 and Penglai 20-2.