The Zaozigou gold deposit lies south of the Xiahe-Hezuo regional fault zone in the western Qinling orogenic belt and contains many intermediate to felsic dikes.Diorite porphyry,quartz diorite porphyry and biotite dior...The Zaozigou gold deposit lies south of the Xiahe-Hezuo regional fault zone in the western Qinling orogenic belt and contains many intermediate to felsic dikes.Diorite porphyry,quartz diorite porphyry and biotite diorite porphyry are mineral-bearing dikes,whereas granite porphyry is unrelated to gold mineralization.To compare the relationship between different dikes and mineralization,this study analyzed the cathodoluminescence(CL)of zircon crystals in all four types of dikes exposed in the Zaozigou deposit,using a zircon typological classification.The formation temperature of the granite porphyry(734°C)was higher than the average temperature of the other three types of dikes(704°C),whereas the former’s alkalinity index(395)was lower than the average alkalinity index of the other three dikes(425).TheΣREE amount of granite porphyry(147.18 ppm)was smaller than the averageΣREE amount of the other three dikes(246.80 ppm)and itsδEu value(0.33)was larger than the averageδEu values of the other three dikes(0.30).The U-Pb ages of zircon in the four types of dikes were relatively consistent with the crystallization ages of approximately 240 Ma,which indicates that all four types of dikes intruded in the Middle Triassic.Compared to the other three ore-bearing dikes,the morphology of the zircon crystals in the barren dikes evolved from S13 to S5 and then returned to S13.These results indicate that the barren dike underwent an increase in temperature and a decrease in alkalinity,which may be an important reason for the absence of mineralization.展开更多
The study of metallogeny includes origin,development,modification,and preservation of mineralisation.The understanding of temporal evolution,and post-mineralisation modification and preservation of mineralisation are ...The study of metallogeny includes origin,development,modification,and preservation of mineralisation.The understanding of temporal evolution,and post-mineralisation modification and preservation of mineralisation are vital for building metallogenic theory and mineral prospecting,but they remain poorly understood and controversial.The Zaozigou deposit is the largest Au deposit in the West Qinling Orogen of central China with a resource of 142 t Au,and offers an excellent opportunity for deciphering the post-mineralisation exhumation and preservation of Au deposit in orogens.Here,we present integrated results from zircon U-Pb(ZUPb),apatite U-Pb(AUPb),apatite fission-track(AFT)and apatite(U-Th-Sm)/He(AHe)dating,thermal history modelling,biotite thermobarometer,and pyrite thermoelectricity of the deposit.The aims of the study are to decipher the temporal history,and post-mineralisation tectonic evolution and exhumation,and to evaluate the degree of exhumation and preservation potential of the deposit.Integrating the newly determined ZUPb(ca.242–238 and 218–201 Ma),AUPb(ca.247–235 Ma),AFT(ca.237–186 Ma),and AHe(ca.131–52 Ma)ages with multiple geo-thermochronological dates published from the Zaozigou deposit,major magmatic and hydrothermal events are recognised during ca.250–233 and230–203 Ma,with two Au mineralisation being deposited at ca.230 and 211 Ma.The Zaozigou area underwent rapid postmagma cooling during ca.250–228 Ma,rapid hydrothermal cooling at ca.219–211 Ma,and episodic post-Triassic cooling pulses.Thermal history modelling indicates rapid cooling at ca.210–170 Ma,slow reheating at ca.170–60 Ma,and enhanced cooling during ca.60–35 and 20–9 Ma at the Zaozigou deposit.In conjunction with the Triassic to Cenozoic tectonic evolution of the West Qinling Orogen,the ca.250–233 Ma magmatism,ca.230 Ma Au mineralisation,and ca.250–228 Ma rapid postmagma cooling are related to the northward subduction of the Mianlue Ocean(Paleo-Tethys Ocean).The ca.211 Ma Au mineralisation and rapid hydrothermal cooling during ca.210–170 Ma are correlated with the collision between the South Qinling Belt and South China Block during ca.220–210 Ma and the post-collisional gravitational collapse during the Jurassic.Prolonged reheating during ca.170–60 Ma is associated with the unconformable deposition of coeval sedimentary sequences.The ca.60–35 and 20–9 Ma enhanced cooling relates to the India-Eurasia collision,the northward growth of Tibetan Plateau,and the intensive East Asian summer monsoon during the Cenozoic.~28%–68%amounts of the Au orebodies in the Zaozigou deposit have been eroded away.In contrast with the estimated post-mineralisation exhumation depth of~4.8 km and reported ore-forming depth of 2–6 km,local portions of the deposit are indicated to be preserved to a depth of over 1 km for Au exploration.Timely supply of post-mineralisation sediments and regional peneplanation during the Jurassic to Cenozoic are important factors for preservation of the deposit.During rapid uplift and exhumation of orogens,sediment-hosted Au mineralisation has highly prospective for prospecting.The study also highlights that multidisciplinary approaches of geo-thermochronology,thermobarometer,and thermoelectricity are effective tools in determining post-mineralisation modification and preservation of orebodies.展开更多
基金supported by projects from the National Natural Science Foundation of China(No.42002098)the Natural Science Foundation of Hebei Province(No.D2020209017,No.D2022107003)+2 种基金China Basic Scientific Research Business Fund Project of the Chinese Academy of Geological Sciences(No.JKY202016)the Innovation and Entrepreneurship Training Program for College Students(No.X2022118)North China University of Science and Technology.
文摘The Zaozigou gold deposit lies south of the Xiahe-Hezuo regional fault zone in the western Qinling orogenic belt and contains many intermediate to felsic dikes.Diorite porphyry,quartz diorite porphyry and biotite diorite porphyry are mineral-bearing dikes,whereas granite porphyry is unrelated to gold mineralization.To compare the relationship between different dikes and mineralization,this study analyzed the cathodoluminescence(CL)of zircon crystals in all four types of dikes exposed in the Zaozigou deposit,using a zircon typological classification.The formation temperature of the granite porphyry(734°C)was higher than the average temperature of the other three types of dikes(704°C),whereas the former’s alkalinity index(395)was lower than the average alkalinity index of the other three dikes(425).TheΣREE amount of granite porphyry(147.18 ppm)was smaller than the averageΣREE amount of the other three dikes(246.80 ppm)and itsδEu value(0.33)was larger than the averageδEu values of the other three dikes(0.30).The U-Pb ages of zircon in the four types of dikes were relatively consistent with the crystallization ages of approximately 240 Ma,which indicates that all four types of dikes intruded in the Middle Triassic.Compared to the other three ore-bearing dikes,the morphology of the zircon crystals in the barren dikes evolved from S13 to S5 and then returned to S13.These results indicate that the barren dike underwent an increase in temperature and a decrease in alkalinity,which may be an important reason for the absence of mineralization.
基金jointly supported by the National Natural Science Foundation of China(Grant Nos.42202077,42473029)the Natural Science Foundation of Gansu Province(Grant Nos.22JR5RA440,20JR10RA630)+1 种基金the Fundamental Research Funds for the Central Universities(Grant No.LZUJBKY-2022-42)the Guiding Special Funds of“Double First-Class(First-Class University&First-Class Disciplines)”of Lanzhou University,China(Grant No.561119201)。
文摘The study of metallogeny includes origin,development,modification,and preservation of mineralisation.The understanding of temporal evolution,and post-mineralisation modification and preservation of mineralisation are vital for building metallogenic theory and mineral prospecting,but they remain poorly understood and controversial.The Zaozigou deposit is the largest Au deposit in the West Qinling Orogen of central China with a resource of 142 t Au,and offers an excellent opportunity for deciphering the post-mineralisation exhumation and preservation of Au deposit in orogens.Here,we present integrated results from zircon U-Pb(ZUPb),apatite U-Pb(AUPb),apatite fission-track(AFT)and apatite(U-Th-Sm)/He(AHe)dating,thermal history modelling,biotite thermobarometer,and pyrite thermoelectricity of the deposit.The aims of the study are to decipher the temporal history,and post-mineralisation tectonic evolution and exhumation,and to evaluate the degree of exhumation and preservation potential of the deposit.Integrating the newly determined ZUPb(ca.242–238 and 218–201 Ma),AUPb(ca.247–235 Ma),AFT(ca.237–186 Ma),and AHe(ca.131–52 Ma)ages with multiple geo-thermochronological dates published from the Zaozigou deposit,major magmatic and hydrothermal events are recognised during ca.250–233 and230–203 Ma,with two Au mineralisation being deposited at ca.230 and 211 Ma.The Zaozigou area underwent rapid postmagma cooling during ca.250–228 Ma,rapid hydrothermal cooling at ca.219–211 Ma,and episodic post-Triassic cooling pulses.Thermal history modelling indicates rapid cooling at ca.210–170 Ma,slow reheating at ca.170–60 Ma,and enhanced cooling during ca.60–35 and 20–9 Ma at the Zaozigou deposit.In conjunction with the Triassic to Cenozoic tectonic evolution of the West Qinling Orogen,the ca.250–233 Ma magmatism,ca.230 Ma Au mineralisation,and ca.250–228 Ma rapid postmagma cooling are related to the northward subduction of the Mianlue Ocean(Paleo-Tethys Ocean).The ca.211 Ma Au mineralisation and rapid hydrothermal cooling during ca.210–170 Ma are correlated with the collision between the South Qinling Belt and South China Block during ca.220–210 Ma and the post-collisional gravitational collapse during the Jurassic.Prolonged reheating during ca.170–60 Ma is associated with the unconformable deposition of coeval sedimentary sequences.The ca.60–35 and 20–9 Ma enhanced cooling relates to the India-Eurasia collision,the northward growth of Tibetan Plateau,and the intensive East Asian summer monsoon during the Cenozoic.~28%–68%amounts of the Au orebodies in the Zaozigou deposit have been eroded away.In contrast with the estimated post-mineralisation exhumation depth of~4.8 km and reported ore-forming depth of 2–6 km,local portions of the deposit are indicated to be preserved to a depth of over 1 km for Au exploration.Timely supply of post-mineralisation sediments and regional peneplanation during the Jurassic to Cenozoic are important factors for preservation of the deposit.During rapid uplift and exhumation of orogens,sediment-hosted Au mineralisation has highly prospective for prospecting.The study also highlights that multidisciplinary approaches of geo-thermochronology,thermobarometer,and thermoelectricity are effective tools in determining post-mineralisation modification and preservation of orebodies.
