Infrared microthermometry allows direct measurement of fluid inclusions hosted in opaque ore minerals and can provide direct constraints on the evolution of ore-forming fluids.This study presents infrared microthermom...Infrared microthermometry allows direct measurement of fluid inclusions hosted in opaque ore minerals and can provide direct constraints on the evolution of ore-forming fluids.This study presents infrared microthermometry of spherite-hosted fluid inclusions from the Xinqiao deposit in the Middle-Lower Yangtze Metallogenic Belt and sheds new light on the ore genesis of the deposit.Considering that infrared light may lead to non-negligible temperature deviations during microthermometry,some tests were first conducted to ensure the accuracy of the microthermometric measurements.The measurement results indicated that using the lowest light intensity of the microscope and inserting an optical filter were effective in minimizing the possible temperature deviations of infrared microthermometry.All sphalerite-hosted fluid inclusions from the Xinqiao deposit were aqueous.They show homogenization temperature ranging from~200 to 350℃,but have two separate salinity groups(1.0 wt%-10 wt%and 15.1 wt%-19.2 wt%NaCl equivalent).The low-salinity group represents sedimentary exhalative(SEDEX)-associated fluids,whereas the high-salinity group results from modification by later magmatic hydrothermal fluids.Combined with published fluid inclusion data,the four-stage fluid evolution of the Xinqiao deposit was depicted.Furthermore,our data suggest that the Xinqiao deposit was formed by twostage metallogenic events including SEDEX and magmatic-hydrothermal mineralization.展开更多
The Xinqiao deposit is located in the Tongling area,Anhui Province.This deposit is dominantly composed of stratiform sulfide orebodies,which are restricted to the transitional zone from clastic rocks to carbonates at ...The Xinqiao deposit is located in the Tongling area,Anhui Province.This deposit is dominantly composed of stratiform sulfide orebodies,which are restricted to the transitional zone from clastic rocks to carbonates at the base of the Late Carboniferous Huanglong Formation.There are discordant veinlets or networks of mineralization in the footwall rocks below the stratiform sulfide orebodies.The underlying discordant mineralization zones coexist with conformable stratiform sulfide orebodies,which are considered to be the most representative features of massive sulfide deposits formed by submarine exhalative sedimentation.This study reports a pyrite 187Re-187Os isotopic age of 319±13 Ma(MSWD=16) for the footwall mineralization zone.This isochron age is consistent with the interval of strata hosting the conformable stratiform sulfide orebody,and provides direct geochronological evidence for Carboniferous exhalative sedimentary mineralization.展开更多
Colloform pyrite(CPy)is widely distributed in the Tongling mineralization cluster of the Middle-Lower Yangtze River Mineralization Belt(MLYRMB),China.There have many debates as to whether such CPy is associated with L...Colloform pyrite(CPy)is widely distributed in the Tongling mineralization cluster of the Middle-Lower Yangtze River Mineralization Belt(MLYRMB),China.There have many debates as to whether such CPy is associated with Late Mesozoic igneous or Carboniferous sedimentation.CPy from the Xinqiao deposit,a representative of the stratabound sulfide deposits in the MLYRMB,was studied by powder X-ray diffraction(XRD),field-emission scanning electron microscopy(SEM),and high-resolution transmission electron microscopy(TEM).The results show that CPy mainly comprises pyrite,pyrrhotite,quartz,and illite.Pyrite in CPy shows cubic,globule,and xenomorphic morphologies.No octahedral or pyritohedron was observed.Most of the quartz crystals display xenomorphic morphology,where pyrite mold are popular on the surface.Organic matter(OM),which is usually bound to illite,is an important component in CPy.Morphological investigations which exhibit detrital features of quartz and clay minerals indicate that they were derived from continental weathering.Specially,some hexagonal pyrrhotite nanoparticles which show mackinawite morphology are coexisted with OM.The results indicate that the transformation process of sulfides possibly is mackinawite(the precursor)—hexagonal pyrrhotite-pyrite.Thus,compositional and micro-textural characteristics of CPy in Xinqiao deposit suggest it to be a sedimentary origin rather than a hydrothermal origin which is associated with Yanshanian magmatism.Moreover,the coexistence of CPy and stratabound sulfide orebodies in the MLYRMB suggests a causal link between the two.It is considered that CPy might have served as a Cu mineralization geochemical barrier for the Cu-bearing ore-forming fluids,which originated from the Mesozoic magma in the MLYRMB.展开更多
基金supported by the National Key R&D Program of China(2018YFA0702701)the Fundamental Research Funds for the Central Universities(WK3410000015).
文摘Infrared microthermometry allows direct measurement of fluid inclusions hosted in opaque ore minerals and can provide direct constraints on the evolution of ore-forming fluids.This study presents infrared microthermometry of spherite-hosted fluid inclusions from the Xinqiao deposit in the Middle-Lower Yangtze Metallogenic Belt and sheds new light on the ore genesis of the deposit.Considering that infrared light may lead to non-negligible temperature deviations during microthermometry,some tests were first conducted to ensure the accuracy of the microthermometric measurements.The measurement results indicated that using the lowest light intensity of the microscope and inserting an optical filter were effective in minimizing the possible temperature deviations of infrared microthermometry.All sphalerite-hosted fluid inclusions from the Xinqiao deposit were aqueous.They show homogenization temperature ranging from~200 to 350℃,but have two separate salinity groups(1.0 wt%-10 wt%and 15.1 wt%-19.2 wt%NaCl equivalent).The low-salinity group represents sedimentary exhalative(SEDEX)-associated fluids,whereas the high-salinity group results from modification by later magmatic hydrothermal fluids.Combined with published fluid inclusion data,the four-stage fluid evolution of the Xinqiao deposit was depicted.Furthermore,our data suggest that the Xinqiao deposit was formed by twostage metallogenic events including SEDEX and magmatic-hydrothermal mineralization.
基金supported by the National Natural Science Foundation of China (40930742 and 40221301)the Key Project of Natural Science Foundation of Jiangsu Province (BK2008026)+1 种基金the National Key Technology R&D Program (2009BAB43B03)a Ph.D. Program from the Foundation of the Ministry of Education of China (1999028435)
文摘The Xinqiao deposit is located in the Tongling area,Anhui Province.This deposit is dominantly composed of stratiform sulfide orebodies,which are restricted to the transitional zone from clastic rocks to carbonates at the base of the Late Carboniferous Huanglong Formation.There are discordant veinlets or networks of mineralization in the footwall rocks below the stratiform sulfide orebodies.The underlying discordant mineralization zones coexist with conformable stratiform sulfide orebodies,which are considered to be the most representative features of massive sulfide deposits formed by submarine exhalative sedimentation.This study reports a pyrite 187Re-187Os isotopic age of 319±13 Ma(MSWD=16) for the footwall mineralization zone.This isochron age is consistent with the interval of strata hosting the conformable stratiform sulfide orebody,and provides direct geochronological evidence for Carboniferous exhalative sedimentary mineralization.
基金supported by the National Natural Science Foundation of China(Grant nos 41672038,41572029,41872043)the National Key Research and Development Program of China(Grant no.2016YFC0600209)。
文摘Colloform pyrite(CPy)is widely distributed in the Tongling mineralization cluster of the Middle-Lower Yangtze River Mineralization Belt(MLYRMB),China.There have many debates as to whether such CPy is associated with Late Mesozoic igneous or Carboniferous sedimentation.CPy from the Xinqiao deposit,a representative of the stratabound sulfide deposits in the MLYRMB,was studied by powder X-ray diffraction(XRD),field-emission scanning electron microscopy(SEM),and high-resolution transmission electron microscopy(TEM).The results show that CPy mainly comprises pyrite,pyrrhotite,quartz,and illite.Pyrite in CPy shows cubic,globule,and xenomorphic morphologies.No octahedral or pyritohedron was observed.Most of the quartz crystals display xenomorphic morphology,where pyrite mold are popular on the surface.Organic matter(OM),which is usually bound to illite,is an important component in CPy.Morphological investigations which exhibit detrital features of quartz and clay minerals indicate that they were derived from continental weathering.Specially,some hexagonal pyrrhotite nanoparticles which show mackinawite morphology are coexisted with OM.The results indicate that the transformation process of sulfides possibly is mackinawite(the precursor)—hexagonal pyrrhotite-pyrite.Thus,compositional and micro-textural characteristics of CPy in Xinqiao deposit suggest it to be a sedimentary origin rather than a hydrothermal origin which is associated with Yanshanian magmatism.Moreover,the coexistence of CPy and stratabound sulfide orebodies in the MLYRMB suggests a causal link between the two.It is considered that CPy might have served as a Cu mineralization geochemical barrier for the Cu-bearing ore-forming fluids,which originated from the Mesozoic magma in the MLYRMB.
