The Hatu large gold deposit is located on the western margin of the Junggar basin, Xinjiang. Its mineralization is characterized by auriferous quartz veins and Au-bearing altered fracturing zones. Studies on mineralog...The Hatu large gold deposit is located on the western margin of the Junggar basin, Xinjiang. Its mineralization is characterized by auriferous quartz veins and Au-bearing altered fracturing zones. Studies on mineralogy, inclusions and decrepitation temperature indicate that the gold deposit was formed by overlapping of two kinds of fluid of different origins, instead of gradual evolution of a single fluid. The auriferous quartz veins are related to magmatism-originated fluid, but the Au-bearing altered fracturing zones to deep-derived fluid. Bonanzas in quartz veins were formed and localized at overlapping positions of two types of fluid under intensive compression.展开更多
The extension of the suture zone between the Siberian and Kazakhstan continents in China has been a matter of debate because few outcrops of ophiolitic melange have been found so far. The recently found Tuerkubantao o...The extension of the suture zone between the Siberian and Kazakhstan continents in China has been a matter of debate because few outcrops of ophiolitic melange have been found so far. The recently found Tuerkubantao ophiolitic melange, which is located east of the Kekesentao Mt. in the Buer- jin County of the Chinese Altay, provides an important clue for this problem. This paper presents the results of field investigation, petrology, U-Pb isotope dating of zircons and bulk-rock geochemistry of the Tuerkubantao melange rocks. The melange consists of fault-contacted ultramafic rocks, gabbro, diabase, basalt, flysch and granitoids. The ultramafic-mafic rocks are Mg-rich （Mg#= 4.25-6.35） and w（SiO2） spans 38.8%--46.8%. Basalt and gabbro are geochemically similar and are characterized by low w（FeOt） （10.9%）, total alkali w（Na20 ＋ K20） = 2.58%） and w（TiO2） （1.17%） and affinity to the Mg-rich tholeiite series. The flat REE and trace-element patterns of the ultramafic-mafic rocks are indic- ative of their ophiolite origin, i.e., formation in a mid-oceanic ridge setting. The fragments of low-K gneissic granite formed in suprasubduction or syn-collisional setting. Zircons from gabbro and gneissic granite yielded U-Pb ages of 363 and 355 Ma, respectively, suggesting Late Devonian mid-oceanic spreading and oceanic subduction accompanied by suprasubduction magmatism. The Tuerkubantao ophiolite together with the Qiaoxiahala and Buergen ophiolites of the Kekesentao belt define an ophiolitic melange belt extending along the Erqis fault. This belt probably belongs to the Ural- Zaisan-South Mongolian suture-shear zone formed during the subduction of the Paleo-Asian Ocean and subsequent collision of the Siberian and Kazakhstan continents.展开更多
The Mesoproterozoic Kunyang rift, which is located on the western margin of the Yangtze platform and the southern section of the Kangdian axis, is a rare massive Precambrian iron-copper polymetallic mineralization zon...The Mesoproterozoic Kunyang rift, which is located on the western margin of the Yangtze platform and the southern section of the Kangdian axis, is a rare massive Precambrian iron-copper polymetallic mineralization zone in China. The Mesoproterozoic Wulu (Wuding-Lufeng) basin in the middle of the rift is an elliptic basin controlled by a ring fracture system. Moreover, volcanic activities in the basin display zonation of an outer ring, a middle ring and an inner ring with carbonatitic volcanic rocks and sub-volcanic dykes discovered in the outer and middle rings. The Sm-Nd isochron ages have been determined for the outer-ring carbonatitic lavas (1685 Ma) and basaltic porphyrite of the radiating dyke swarm (1645 Ma) and the Rb-Sr isochron ages for the out-ring carbonatitic lavas (893 Ma) and the middle-ring dykes (1048 Ma). In combination of the U-Pb concordant ages of zircon (1743 Ma) in trachy-andesite of the corresponding period and stratum (1569 Ma) of the Etouchang Formation, as well as the Rb-Sr isochron age (1024 Ma) and K-Ar age (1186 Ma) of the dykes in the middle ring, the age of carbonarites in the basin is preliminarily determined. It is ensured that all of these carbonatites were formed in the Mesoprotero/oic period, whereby two stages could be identified as follows: in the first stage, carbonatitic volcanic groups, such as lavas, pyroclastic rocks and volcaniclastic sedimentary rocks, were formed in the outer ring; in the second stage, carbonatitic breccias and dykes appeared in the middle ring. The metamorphic age of the carbonatitic lavas in the outer ring was determined to be concurrent with the end of the first stage of the Neoproterozoic period, corresponding to the Jinning movement in central Yunnan.展开更多
Zircons from the auriferous quartz vein in the Rushan gold deposit, Jiaodong Peninsula, have high common Pb contents (206Pbc = 2.00%—15.88%) and Th/U ratios (0.31—1.35), and trap primary CO2-H2O fluid inclusion simi...Zircons from the auriferous quartz vein in the Rushan gold deposit, Jiaodong Peninsula, have high common Pb contents (206Pbc = 2.00%—15.88%) and Th/U ratios (0.31—1.35), and trap primary CO2-H2O fluid inclusion similar to ore-forming fluids, indicating that they grew from high Th/U ratio ore-forming fluids responsible for gold min- eralization. SHRIMP U-Pb analyses of these zircons gave an age of 117±3 Ma comparable with the ages reported by the former researches in the other areas in the Jiaodong Penin- sula, which is interpreted as the age of gold mineralization at Rushan. The age of SHRIMP zircon U-Pb dating with 160±3 Ma from host rock Kunyushan monzogranite is different from that of the gold mineralization, indicating that there is no genetic relationship between gold mineralization and the granitic magmatism. SHRIMP U-Pb dating on hydrothermal zircons from auriferous quartz veins could be used to con- strain the timing of lode gold mineralization and the rela- tionship to relevant hydrothermal event.展开更多
基金the 973 National Project(grant 2001cb409806) the National Natural Science Foundation of China(grant 40273021).
文摘The Hatu large gold deposit is located on the western margin of the Junggar basin, Xinjiang. Its mineralization is characterized by auriferous quartz veins and Au-bearing altered fracturing zones. Studies on mineralogy, inclusions and decrepitation temperature indicate that the gold deposit was formed by overlapping of two kinds of fluid of different origins, instead of gradual evolution of a single fluid. The auriferous quartz veins are related to magmatism-originated fluid, but the Au-bearing altered fracturing zones to deep-derived fluid. Bonanzas in quartz veins were formed and localized at overlapping positions of two types of fluid under intensive compression.
基金supported by the Major State Basic Research Program of the People's Republic of China(Nos.2007CB411304 and 2001CB409806)
文摘The extension of the suture zone between the Siberian and Kazakhstan continents in China has been a matter of debate because few outcrops of ophiolitic melange have been found so far. The recently found Tuerkubantao ophiolitic melange, which is located east of the Kekesentao Mt. in the Buer- jin County of the Chinese Altay, provides an important clue for this problem. This paper presents the results of field investigation, petrology, U-Pb isotope dating of zircons and bulk-rock geochemistry of the Tuerkubantao melange rocks. The melange consists of fault-contacted ultramafic rocks, gabbro, diabase, basalt, flysch and granitoids. The ultramafic-mafic rocks are Mg-rich （Mg#= 4.25-6.35） and w（SiO2） spans 38.8%--46.8%. Basalt and gabbro are geochemically similar and are characterized by low w（FeOt） （10.9%）, total alkali w（Na20 ＋ K20） = 2.58%） and w（TiO2） （1.17%） and affinity to the Mg-rich tholeiite series. The flat REE and trace-element patterns of the ultramafic-mafic rocks are indic- ative of their ophiolite origin, i.e., formation in a mid-oceanic ridge setting. The fragments of low-K gneissic granite formed in suprasubduction or syn-collisional setting. Zircons from gabbro and gneissic granite yielded U-Pb ages of 363 and 355 Ma, respectively, suggesting Late Devonian mid-oceanic spreading and oceanic subduction accompanied by suprasubduction magmatism. The Tuerkubantao ophiolite together with the Qiaoxiahala and Buergen ophiolites of the Kekesentao belt define an ophiolitic melange belt extending along the Erqis fault. This belt probably belongs to the Ural- Zaisan-South Mongolian suture-shear zone formed during the subduction of the Paleo-Asian Ocean and subsequent collision of the Siberian and Kazakhstan continents.
基金supported by a key project of resources and environment of the Chinese Academy of Sciences(No:KZ951-B1-404)the Project 211 of the China University of Geosciences
文摘The Mesoproterozoic Kunyang rift, which is located on the western margin of the Yangtze platform and the southern section of the Kangdian axis, is a rare massive Precambrian iron-copper polymetallic mineralization zone in China. The Mesoproterozoic Wulu (Wuding-Lufeng) basin in the middle of the rift is an elliptic basin controlled by a ring fracture system. Moreover, volcanic activities in the basin display zonation of an outer ring, a middle ring and an inner ring with carbonatitic volcanic rocks and sub-volcanic dykes discovered in the outer and middle rings. The Sm-Nd isochron ages have been determined for the outer-ring carbonatitic lavas (1685 Ma) and basaltic porphyrite of the radiating dyke swarm (1645 Ma) and the Rb-Sr isochron ages for the out-ring carbonatitic lavas (893 Ma) and the middle-ring dykes (1048 Ma). In combination of the U-Pb concordant ages of zircon (1743 Ma) in trachy-andesite of the corresponding period and stratum (1569 Ma) of the Etouchang Formation, as well as the Rb-Sr isochron age (1024 Ma) and K-Ar age (1186 Ma) of the dykes in the middle ring, the age of carbonarites in the basin is preliminarily determined. It is ensured that all of these carbonatites were formed in the Mesoprotero/oic period, whereby two stages could be identified as follows: in the first stage, carbonatitic volcanic groups, such as lavas, pyroclastic rocks and volcaniclastic sedimentary rocks, were formed in the outer ring; in the second stage, carbonatitic breccias and dykes appeared in the middle ring. The metamorphic age of the carbonatitic lavas in the outer ring was determined to be concurrent with the end of the first stage of the Neoproterozoic period, corresponding to the Jinning movement in central Yunnan.
文摘Zircons from the auriferous quartz vein in the Rushan gold deposit, Jiaodong Peninsula, have high common Pb contents (206Pbc = 2.00%—15.88%) and Th/U ratios (0.31—1.35), and trap primary CO2-H2O fluid inclusion similar to ore-forming fluids, indicating that they grew from high Th/U ratio ore-forming fluids responsible for gold min- eralization. SHRIMP U-Pb analyses of these zircons gave an age of 117±3 Ma comparable with the ages reported by the former researches in the other areas in the Jiaodong Penin- sula, which is interpreted as the age of gold mineralization at Rushan. The age of SHRIMP zircon U-Pb dating with 160±3 Ma from host rock Kunyushan monzogranite is different from that of the gold mineralization, indicating that there is no genetic relationship between gold mineralization and the granitic magmatism. SHRIMP U-Pb dating on hydrothermal zircons from auriferous quartz veins could be used to con- strain the timing of lode gold mineralization and the rela- tionship to relevant hydrothermal event.
