The time gap between diagenesis and mineralization (TGDM) for comagmatic gold deposits (CGD) plays an important role in confirming the genetic relationship between gold deposits and their related intrusions. With the ...The time gap between diagenesis and mineralization (TGDM) for comagmatic gold deposits (CGD) plays an important role in confirming the genetic relationship between gold deposits and their related intrusions. With the help of preciously published isotopic ages of some typical gold deposits and their related rocks in China,the authors have discussed and quantified the distribution characteristics and scope of the TGDM. Statistical analyses and Kolmogorov tests showed that mineralizing events are either contemporaneous with or slightly postdate their cognate magma. The TGDM conforms with normal distributions at a 0.05 confidence level and clusters between 0 and 16.0 Ma with a mean of 7.0 Ma. Thus,if the TGDM of CGD is less than 16.0 Ma,it is reasonable to consider,with the aid of other evidence,the possibility of its comagmatic genetic affiliation. The authors also emphasized that to get a precise time gap it is necessary to strengthen the diagenesis-mineralization geological background of the deposits studied,and to pay attention to the study of time gap in combination with trace elements and isotope tracing.展开更多
The Kunlunguan biotite granite pluton, located in the southwestern part of the Nanling Mesozoic granite belt, is controlled by the NW-trending Nandan-Kunlunguan deep fault. LA-ICP-MS zircon U-Pb dating yielded a weigh...The Kunlunguan biotite granite pluton, located in the southwestern part of the Nanling Mesozoic granite belt, is controlled by the NW-trending Nandan-Kunlunguan deep fault. LA-ICP-MS zircon U-Pb dating yielded a weighted mean 206Pb/238U age of 93.0±1 Ma (MSDW=1.7) for the main part of the pluton, implying its Late Creta-ceous intrusion. The Kunlunguan body is a high-K calc-alkaline rock characterized by high silicon, alkali and alu-minum, and low phosphorus and titanium. SiO2 contents of the Kunlunguan body range from 68.13% to 72.61% and K2O/Na2O ratios from 1.28 to 1.87. A/CNK values vary from 0.76 to 1.42, indicating a metaluminous to intensively peraluminous character. The rocks are enriched in Ga, Rb, Th, U and Pb but depleted in Ba, Nb, Sr, P and Ti. The REEs are characterized by remarkable negative Eu anomalies (Eu/Eu*=0.53-0.73) and exhibit right-inclined "V"-shaped patterns with LREE enrichment. Petrology, major and trace elements data all indicate that the pluton is aluminous A-type granite which intruded in a post-collisional extensional tectonic setting. It is related to back-arc extension, reflecting high-angle subduction of the paleo-Pacific plate, caused by northward movement of the Indian plate. The Nandan-Kunlunguan A-type granites belt, together with similar plutons in the coastal areas of Zhejiang and Fujian provinces, represent the two A-type granite belts under a matching tectonic system.展开更多
基金supported by the Doctoral Education Program Fund of the Ministry of Education,Peoples Republic of China (No. 20040491502)
文摘The time gap between diagenesis and mineralization (TGDM) for comagmatic gold deposits (CGD) plays an important role in confirming the genetic relationship between gold deposits and their related intrusions. With the help of preciously published isotopic ages of some typical gold deposits and their related rocks in China,the authors have discussed and quantified the distribution characteristics and scope of the TGDM. Statistical analyses and Kolmogorov tests showed that mineralizing events are either contemporaneous with or slightly postdate their cognate magma. The TGDM conforms with normal distributions at a 0.05 confidence level and clusters between 0 and 16.0 Ma with a mean of 7.0 Ma. Thus,if the TGDM of CGD is less than 16.0 Ma,it is reasonable to consider,with the aid of other evidence,the possibility of its comagmatic genetic affiliation. The authors also emphasized that to get a precise time gap it is necessary to strengthen the diagenesis-mineralization geological background of the deposits studied,and to pay attention to the study of time gap in combination with trace elements and isotope tracing.
基金supported by the Program for Changjiang Schoolars and Innovative Research Team in University (IRT0755)the Key Laboratory of Geological Progress and Mineral Resources (GPMR),China University of Geosciences
文摘The Kunlunguan biotite granite pluton, located in the southwestern part of the Nanling Mesozoic granite belt, is controlled by the NW-trending Nandan-Kunlunguan deep fault. LA-ICP-MS zircon U-Pb dating yielded a weighted mean 206Pb/238U age of 93.0±1 Ma (MSDW=1.7) for the main part of the pluton, implying its Late Creta-ceous intrusion. The Kunlunguan body is a high-K calc-alkaline rock characterized by high silicon, alkali and alu-minum, and low phosphorus and titanium. SiO2 contents of the Kunlunguan body range from 68.13% to 72.61% and K2O/Na2O ratios from 1.28 to 1.87. A/CNK values vary from 0.76 to 1.42, indicating a metaluminous to intensively peraluminous character. The rocks are enriched in Ga, Rb, Th, U and Pb but depleted in Ba, Nb, Sr, P and Ti. The REEs are characterized by remarkable negative Eu anomalies (Eu/Eu*=0.53-0.73) and exhibit right-inclined "V"-shaped patterns with LREE enrichment. Petrology, major and trace elements data all indicate that the pluton is aluminous A-type granite which intruded in a post-collisional extensional tectonic setting. It is related to back-arc extension, reflecting high-angle subduction of the paleo-Pacific plate, caused by northward movement of the Indian plate. The Nandan-Kunlunguan A-type granites belt, together with similar plutons in the coastal areas of Zhejiang and Fujian provinces, represent the two A-type granite belts under a matching tectonic system.
