This paper presents the results of a set of numerical models focussing on structural controls on hydrothermal mineralization. We first give an overview of natural phenomena of structurally-controlled ore formation and...This paper presents the results of a set of numerical models focussing on structural controls on hydrothermal mineralization. We first give an overview of natural phenomena of structurally-controlled ore formation and the background theory and mechanisms for such controls. We then provide the results of a group of simple 2D numerical models validated through comparison with Cu-vein structure observed near the Shilu Copper deposit (Yangchun, Guangdong Province, China) and finally a case study of 3D numerical modelling applied to the Hodgkinson Province in North Queensland (Australia). Two modelling approaches, discrete deformation modelling and continuum coupled deformation and fluid flow modelling, are involved. The 2D model-derived patterns are remarkably consistent with the Cu-vein structure from the Shilu Copper deposit, and show that both modelling approaches can realistically simulate the mechanical behaviours of shear and dilatant fractures. The continuum coupled deformation and fluid flow model indicates that pattern of the Cu- veins near the Shilu deposit is the result of shear strain localization, development of dilation and fluid focussing into the dilatant fracture segments. The 3D case-study models (with deformation and fluid flow coupling) on the Hodgkinson Province generated a number of potential gold mineralization展开更多
Magnetite separates from the Shaquanzi Fe-Cu deposit in the eastern Tianshan are used for Re-Os geochronological study. Re-Os data show that magnetite separates contain ca. 0.7 to 50.9 ppb Re and ca. 16 to 63 ppt Os. ...Magnetite separates from the Shaquanzi Fe-Cu deposit in the eastern Tianshan are used for Re-Os geochronological study. Re-Os data show that magnetite separates contain ca. 0.7 to 50.9 ppb Re and ca. 16 to 63 ppt Os. Eight samples yield a model 3 isochron age of (303 ±12) Ma (2or), which is within uncertainty consistent with of the Re-Os date (295±7 Ma) of associated pyrite. Tectonic evolution shows that the Late Carboniferous Aqishan-Yamansu belt was a back-arc rift. Therefore, the Re-Os age of ca. 300 Ma indicates that the Shaquanzi Fe-Cu deposit may have formed in a back-arc extensional environment and was closely related to mantle-derived magmatism. The successful application of Re-Os magnetite geochronology in the Shaquanzi Fe-Cu deposit suggests that the purity of magnetite, relatively high Re and Os contents, and the closure of Re-Os systematic are base factors for a successful Re-Os geochronology. There would be a good prospect for Re-Os geochronology for magnet- ite.展开更多
The Eastern Kunlun Orogenic Belt(EKOB)has a complex geological structure and diverse magmatic activities,which are closely related to the Qaidam Basin and the Tethys tectonic evolution.There are at least 3 stages mafi...The Eastern Kunlun Orogenic Belt(EKOB)has a complex geological structure and diverse magmatic activities,which are closely related to the Qaidam Basin and the Tethys tectonic evolution.There are at least 3 stages mafic-ultramafic rocks occurred in the Early Paleozoic in EKOB.The first stage is the Later-Silurian to Early Devonian,represented by the giant Xiarihamu super large magmatic Cu-Ni deposit,containing about 1.18 million metric tons(Mt)of nickel with average grades of 0.65%Ni,and its age of ore-forming pyroxene peridotite is 411 Ma;The second stage is the Early Carboniferous,represented by the large Shitoukengde magmatic Cu-Ni sulfide deposit,and its ore-forming age of the olivine websterite is 334 Ma;The third stage of mafic-ultramafic rocks occurred mainly during the Middle-Late Triassic,represented by Xiaojianshan,Lalinggaoli,and Kaimuqi complexes,and no economical ore bodies have been found in this period.The authors summarized the difference between the ore-bearing and the nonmineralized mafic-ultramafic rocks in the EKOB.The olivine of the ore-bearing complexes contains higher MgO and SiO2 content but lower FeO and CaO contents,and the clinopyroxene of ore-bearing complexes contains lower FeO and CaO contents.Crustal sulfur contamination is key to the formation of the giant Xiarihamu Ni deposit,and crustal sulfur contamination degree of the giant magmatic Ni deposit is higher than that of large Ni deposit.The above indicators could guide the exploration and evaluation of similar deposits in the EKOB.展开更多
Porphyry copper±molybdenum±gold deposits(PCDs) are the most representative magmatic-hydrothermal metallogenic system above subduction zones with important economic value. Previous studies revealed that large...Porphyry copper±molybdenum±gold deposits(PCDs) are the most representative magmatic-hydrothermal metallogenic system above subduction zones with important economic value. Previous studies revealed that large PCDs are generally formed from initial arc magmas(from subduction-induced partial melting of the mantle wedge), which eventually ascend to the shallow crust(3–5 km) for mineralization after a series of complex evolution processes. These processes include(1) the dehydration or partial melting of subducting slab, which induces partial melting of the metasomatized mantle wedge;(2)the ascent of mantle-derived magma to the bottom of the lower crust, which subsequently undergoes crustal processes such as assimilation plus fractional crystallization(AFC) or melting, assimilation, storage and homogenization(MASH);(3) the magma chamber formation at the bottom of the lower, middle and upper crust;(4) the final emplacement and volatilization of porphyry stocks;and(5) the accumulation of ore-forming fluids and metal precipitation. Despite the many decades of research, many issues involving the PCD metallogenic mechanism still remain to resolve, such as(1) the tectonic control on the geochemical characteristics of ore-forming magma;(2) the reason for the different lifespans of the long-term magmatic arc evolution and geologically "instantaneous" mineralization processes;(3) the source of ore-forming materials;(4) the relative contributions of metal pre-enrichment to mineralization by the magma source and by magmatic evolution;and(5) the decoupling behaviors of Cu and Au during the pre-enrichment. These issues point out the direction for future PCD metallogenic research, and the resolution to them will deepen our understanding of the metallogenesis at convergent plate boundaries.展开更多
文摘This paper presents the results of a set of numerical models focussing on structural controls on hydrothermal mineralization. We first give an overview of natural phenomena of structurally-controlled ore formation and the background theory and mechanisms for such controls. We then provide the results of a group of simple 2D numerical models validated through comparison with Cu-vein structure observed near the Shilu Copper deposit (Yangchun, Guangdong Province, China) and finally a case study of 3D numerical modelling applied to the Hodgkinson Province in North Queensland (Australia). Two modelling approaches, discrete deformation modelling and continuum coupled deformation and fluid flow modelling, are involved. The 2D model-derived patterns are remarkably consistent with the Cu-vein structure from the Shilu Copper deposit, and show that both modelling approaches can realistically simulate the mechanical behaviours of shear and dilatant fractures. The continuum coupled deformation and fluid flow model indicates that pattern of the Cu- veins near the Shilu deposit is the result of shear strain localization, development of dilation and fluid focussing into the dilatant fracture segments. The 3D case-study models (with deformation and fluid flow coupling) on the Hodgkinson Province generated a number of potential gold mineralization
基金financially supported by the National Basic Research Program of China(Grant No.2012CB416804)the ‘‘CAS Hundred Talents’’ Project from the Chinese Academy of Sciences(Grant No.KZCX2-YW-BR-09)to Qi Liang
文摘Magnetite separates from the Shaquanzi Fe-Cu deposit in the eastern Tianshan are used for Re-Os geochronological study. Re-Os data show that magnetite separates contain ca. 0.7 to 50.9 ppb Re and ca. 16 to 63 ppt Os. Eight samples yield a model 3 isochron age of (303 ±12) Ma (2or), which is within uncertainty consistent with of the Re-Os date (295±7 Ma) of associated pyrite. Tectonic evolution shows that the Late Carboniferous Aqishan-Yamansu belt was a back-arc rift. Therefore, the Re-Os age of ca. 300 Ma indicates that the Shaquanzi Fe-Cu deposit may have formed in a back-arc extensional environment and was closely related to mantle-derived magmatism. The successful application of Re-Os magnetite geochronology in the Shaquanzi Fe-Cu deposit suggests that the purity of magnetite, relatively high Re and Os contents, and the closure of Re-Os systematic are base factors for a successful Re-Os geochronology. There would be a good prospect for Re-Os geochronology for magnet- ite.
基金This study was financially supported by the Special Fund for Land and Resources Scientific Research of Public Interest(201511020)the Natural Science Foundation of Shaanxi Province(2017JM4002)Natural Science Foundation of China(41873053).
文摘The Eastern Kunlun Orogenic Belt(EKOB)has a complex geological structure and diverse magmatic activities,which are closely related to the Qaidam Basin and the Tethys tectonic evolution.There are at least 3 stages mafic-ultramafic rocks occurred in the Early Paleozoic in EKOB.The first stage is the Later-Silurian to Early Devonian,represented by the giant Xiarihamu super large magmatic Cu-Ni deposit,containing about 1.18 million metric tons(Mt)of nickel with average grades of 0.65%Ni,and its age of ore-forming pyroxene peridotite is 411 Ma;The second stage is the Early Carboniferous,represented by the large Shitoukengde magmatic Cu-Ni sulfide deposit,and its ore-forming age of the olivine websterite is 334 Ma;The third stage of mafic-ultramafic rocks occurred mainly during the Middle-Late Triassic,represented by Xiaojianshan,Lalinggaoli,and Kaimuqi complexes,and no economical ore bodies have been found in this period.The authors summarized the difference between the ore-bearing and the nonmineralized mafic-ultramafic rocks in the EKOB.The olivine of the ore-bearing complexes contains higher MgO and SiO2 content but lower FeO and CaO contents,and the clinopyroxene of ore-bearing complexes contains lower FeO and CaO contents.Crustal sulfur contamination is key to the formation of the giant Xiarihamu Ni deposit,and crustal sulfur contamination degree of the giant magmatic Ni deposit is higher than that of large Ni deposit.The above indicators could guide the exploration and evaluation of similar deposits in the EKOB.
基金supported by the National Natural Science Foundation of China for Distinguished Young Scholars(Grant No.41725009)the“135”Planned Project of Guangzhou Institute of Geochemistry,Chinese Academy of Sciences(Grant No.135PY201606)the Strategic Priority Program of the Chinese Academy of Sciences(Type B)(Grant No.XDB18030206)。
文摘Porphyry copper±molybdenum±gold deposits(PCDs) are the most representative magmatic-hydrothermal metallogenic system above subduction zones with important economic value. Previous studies revealed that large PCDs are generally formed from initial arc magmas(from subduction-induced partial melting of the mantle wedge), which eventually ascend to the shallow crust(3–5 km) for mineralization after a series of complex evolution processes. These processes include(1) the dehydration or partial melting of subducting slab, which induces partial melting of the metasomatized mantle wedge;(2)the ascent of mantle-derived magma to the bottom of the lower crust, which subsequently undergoes crustal processes such as assimilation plus fractional crystallization(AFC) or melting, assimilation, storage and homogenization(MASH);(3) the magma chamber formation at the bottom of the lower, middle and upper crust;(4) the final emplacement and volatilization of porphyry stocks;and(5) the accumulation of ore-forming fluids and metal precipitation. Despite the many decades of research, many issues involving the PCD metallogenic mechanism still remain to resolve, such as(1) the tectonic control on the geochemical characteristics of ore-forming magma;(2) the reason for the different lifespans of the long-term magmatic arc evolution and geologically "instantaneous" mineralization processes;(3) the source of ore-forming materials;(4) the relative contributions of metal pre-enrichment to mineralization by the magma source and by magmatic evolution;and(5) the decoupling behaviors of Cu and Au during the pre-enrichment. These issues point out the direction for future PCD metallogenic research, and the resolution to them will deepen our understanding of the metallogenesis at convergent plate boundaries.