The late-Paleozoic mafic volcanic rocks occurring in the surrounding areas of the Gonghe basin are distributed in the A'nyêmaqên ophiolite zone, Zongwulong tectonic zone and Kuhai-Saishitang volcanic zon...The late-Paleozoic mafic volcanic rocks occurring in the surrounding areas of the Gonghe basin are distributed in the A'nyêmaqên ophiolite zone, Zongwulong tectonic zone and Kuhai-Saishitang volcanic zone. The mafic volcanics in the A'nyêmaqên zone formed an ancient ridge-centered hotspot around the Majixueshan OIB, the Kuhai-Saishitang mafic rocks consist of E-MORB and continental rift basalts and the Zongwulong volcanic rocks are enriched N-MORB. The regionally low Nb/U and Ce/Pb ratios reflect the influence of the OIB material on the mafic magma source. From geochemistry, spatial distribution and tectonic relationship of the mafic rocks, an ancient triple-junction centered at the Majixueshan can be inferred. The existence of the Kuhai-Saishitang aulacogen may have provided a tectonic channel for the Majixueshan OIB materials metasomatizing the magma source for the Zongwulong rocks. The formation of the triple-junction and the rifting of the Zongwulong zone have separated the orogens and massifs in the region.展开更多
The Changning-Menglian suture in SW Yunnan has been accepted as the Paleotethyan main ocean. However, it has been a matter of debate as to its southerly extension in NW Thailand（the Chiang Mai-Chiang Rai vs. Nan-Utta...The Changning-Menglian suture in SW Yunnan has been accepted as the Paleotethyan main ocean. However, it has been a matter of debate as to its southerly extension in NW Thailand（the Chiang Mai-Chiang Rai vs. Nan-Uttaradit zone）. Our field investigation identified the high-iron basaltic rocks in the Chiang Dao Permian standard profile in NW Thailand. The high-iron rocks provide crucial records for understanding the controversy on the location of Paleotethyan main ocean in NW Thailand. The Early Permian high-iron samples show extremely high Fe Ot（20.96 wt.%–25.56 wt.%） and TiO2（6.07 wt.%–6.34 wt.%） and low SiO2（38.54 wt.%–43.46 wt.%） and Mg O（1.61 wt.%–2.40 wt.%） contents. Such characteristics are similar to those of the Fenner differentiation trend rarely observed in the natural system, distinct from those of the ＂normal＂ Bowen trend. Their chondrite- normalized REE and primitive mantle-normalized patterns are generally similar to those of typical OIB. The initial 87Sr/86 Sr ratios and εNd（t） values range from 0.704 677 to 0.705 103 and 3.16 to 3.48, respectively, falling near the field of typical OIB（oceanic-island basalt）. These data synthetically suggest that the Chiang Dao high-iron rocks are the products of high-degree partial melting of peridotite with Fe-rich eclogitic blobs/streaks in response to a seamount setting. In comparison with the Permian tectonic setting in SW Yunnan and NW Thailand, it is inferred that the Paleotethyan Ocean was located between the Shan-Thai terrane of Sibumasu and Sukhothai arc along the Inthanon zone of the Chiang Mai-Chiang Rai rather than Nan-Uttaradit zones.展开更多
The basement of the Romanian Carpathians is made of Neoproterozoic to early Paleozoic peri- Gondwanan terranes variably involved in the Variscan orogeny, similarly to other basement terrains of Europe. They were hardl...The basement of the Romanian Carpathians is made of Neoproterozoic to early Paleozoic peri- Gondwanan terranes variably involved in the Variscan orogeny, similarly to other basement terrains of Europe. They were hardly dismembered during the Alpine orogeny and traditionally have their own names in the three Carpathian areas. The Danubian domain of the South Carpathians comprises the Dragsan and Lainici-Paiius peri-Amazonian terranes. The Dragsan terrane originated within the ocean surrounding Rodinia and docked with Rodinia at -800 Ma. It does not contain Cadomian magmatism and consequently it is classified as an Avalonian extra-Cadomian terrane, The Lainici-Pfiius terrane is a Ganderian fragment strongly modified by Cadomian subduction-related magmatism, It is attached to the Moesia platform. The TisoviD terrane is an ophiolite that marks the boundary between Drfagsan and Lainici-Paius terranes. The other basement terranes of the Romanian Carpathians originated close to the Ordovician North- African orogen, as a result of the eastern Rheic Ocean opening and closure. Except for the Sebes-Lotru terrane that includes a lower metamorphic unit of Cadomian age, all the other terranes （Bretila, Tulghes, Negrisoara and Rebra in the East Carpathians, Somes, Biharia and Baia de Aries in the Apuseni mountains, Fagaras, Leaota, Carat and Pades in the South Carpathians） represent late Cambrian-Ordovician rock assemblages. Their provenance, is probably within paleo-nortbeast Africa, close to the Arabian-Nubian shield. The late Cambrian-Ordovician terranes are defined here as Carpathian-type terranes. According to their lithostratigraphy and origin, some are of continental margin magmatic arc setting, whereas others formed in rift and back-arc environment and closed to passive continental margin settings. In a paleo- geographic reconstruction, the continental margin magmatic arc terranes were first that drifted out, followed by the passive continental margin terranes with the back-arc terranes in their front. They accreted to Laurussia during the Variscan orogeny. Some of them （Sebes-Lotru in South Carpathians and Baia de Aries in Apuseni mountains） underwent eclogite-grade metamorphism. The Danubian terranes, the Bretila terrane and the Somes terrane were intruded by Variscan granitoids.展开更多
Volcanic rocks in the Bangxi-Chenxing tectonic zone provide important carries for better understanding the Late Paleozoic tectonic evolution in Hainan and its temporal-spatial pattern of the eastern Paleotethyan evolu...Volcanic rocks in the Bangxi-Chenxing tectonic zone provide important carries for better understanding the Late Paleozoic tectonic evolution in Hainan and its temporal-spatial pattern of the eastern Paleotethyan evolution. This paper presents a set of new geochronological and geochemical data on the andesitic and dacitic rocks along the Bangxi-Chenxing tectonic zone in central Hainan. The rep- resentative andesitic and dacitic samples yield similar zircon U-Pb ages of 353^-3 and 351^-7 Ma, respec- tively, being of Early Carboniferous origin. These volcanic rocks are characterized by low TiO2 and high A1203 contents and are enriched in LILEs and LREEs but depletion in HFSEs, along with negative fNd（t） Values of =1.4-- -4.7 and high STSr/S6Sr（i） ratios of 0.707 2-0.710 1. Geochemical signatures suggest that the andesitic and dacitic samples might originate from a metasomatized wedge modified by the slab-derived component in a continental arc setting. In combination with the available data, it is pro- posed for the development of a Carboniferous continental arc in response to the eastern Paleotethyan evolution. The Bangxi-Chenxing tectonic zone might westerly link with the Jinshajiang-Ailaoshan-Song Ma suture zone, constituting an assemblage boundary between the South China and Indochina blocks.展开更多
The foramtion and evolution of collisional orogen is a prominent feature along convergent plate margins, and is generally a complex process. This article presents an integrated study of zircon genesis, U-Pb age and Lu...The foramtion and evolution of collisional orogen is a prominent feature along convergent plate margins, and is generally a complex process. This article presents an integrated study of zircon genesis, U-Pb age and Lu-Hf isotope composition as well as geological characteristics for the western Dabie orogen to constrain its multi-stage evolution history. The results suggest that the formation of oceanic crust in the Huwan area was constrained at ca. 400―430 Ma, which was slightly later than the collision of the northern Qinling with the North China Block. It formed in a marginal basin in the northern margin of the Yangtze Block. The peak metamorphism of eclogite in the Huwan area occurred at ca. 310 Ma, and the timing of the initial exhumation of oceanic eclogite was about 270 Ma. The high to ultrahigh pressure (HP-UHP) metamorphic rocks in the Xinxian and the Hong'an metamorphic zones have the same ages and natures as those of the HP-UHP metamorphic rocks in the other Dabie-Sulu terrains, and also have experienced multi-stage exhumation, and thus can be taken as a coherent part of the Dabie-Sulu orogen. Therefore, the Qinling-Dabie-Sulu orogen is a typical multi-stage continental collision orogen, with an amalgamation process extending more than 200 Ma.展开更多
基金Supported by the National Natural Science Foundation of China (Grant Nos. 40572138 and 40234041)
文摘The late-Paleozoic mafic volcanic rocks occurring in the surrounding areas of the Gonghe basin are distributed in the A'nyêmaqên ophiolite zone, Zongwulong tectonic zone and Kuhai-Saishitang volcanic zone. The mafic volcanics in the A'nyêmaqên zone formed an ancient ridge-centered hotspot around the Majixueshan OIB, the Kuhai-Saishitang mafic rocks consist of E-MORB and continental rift basalts and the Zongwulong volcanic rocks are enriched N-MORB. The regionally low Nb/U and Ce/Pb ratios reflect the influence of the OIB material on the mafic magma source. From geochemistry, spatial distribution and tectonic relationship of the mafic rocks, an ancient triple-junction centered at the Majixueshan can be inferred. The existence of the Kuhai-Saishitang aulacogen may have provided a tectonic channel for the Majixueshan OIB materials metasomatizing the magma source for the Zongwulong rocks. The formation of the triple-junction and the rifting of the Zongwulong zone have separated the orogens and massifs in the region.
基金Financial supports from the National Natural Science Foundation of China(Nos.41190073 and 41402165the Fundamental Research Funds for the Central Universities to SYSU are gratefully acknowledged
文摘The Changning-Menglian suture in SW Yunnan has been accepted as the Paleotethyan main ocean. However, it has been a matter of debate as to its southerly extension in NW Thailand（the Chiang Mai-Chiang Rai vs. Nan-Uttaradit zone）. Our field investigation identified the high-iron basaltic rocks in the Chiang Dao Permian standard profile in NW Thailand. The high-iron rocks provide crucial records for understanding the controversy on the location of Paleotethyan main ocean in NW Thailand. The Early Permian high-iron samples show extremely high Fe Ot（20.96 wt.%–25.56 wt.%） and TiO2（6.07 wt.%–6.34 wt.%） and low SiO2（38.54 wt.%–43.46 wt.%） and Mg O（1.61 wt.%–2.40 wt.%） contents. Such characteristics are similar to those of the Fenner differentiation trend rarely observed in the natural system, distinct from those of the ＂normal＂ Bowen trend. Their chondrite- normalized REE and primitive mantle-normalized patterns are generally similar to those of typical OIB. The initial 87Sr/86 Sr ratios and εNd（t） values range from 0.704 677 to 0.705 103 and 3.16 to 3.48, respectively, falling near the field of typical OIB（oceanic-island basalt）. These data synthetically suggest that the Chiang Dao high-iron rocks are the products of high-degree partial melting of peridotite with Fe-rich eclogitic blobs/streaks in response to a seamount setting. In comparison with the Permian tectonic setting in SW Yunnan and NW Thailand, it is inferred that the Paleotethyan Ocean was located between the Shan-Thai terrane of Sibumasu and Sukhothai arc along the Inthanon zone of the Chiang Mai-Chiang Rai rather than Nan-Uttaradit zones.
基金grant IDEI-PN-II-ID-PCE-2011-30100 from the Romanian National Science Foundation(ANCS-CNCS)
文摘The basement of the Romanian Carpathians is made of Neoproterozoic to early Paleozoic peri- Gondwanan terranes variably involved in the Variscan orogeny, similarly to other basement terrains of Europe. They were hardly dismembered during the Alpine orogeny and traditionally have their own names in the three Carpathian areas. The Danubian domain of the South Carpathians comprises the Dragsan and Lainici-Paiius peri-Amazonian terranes. The Dragsan terrane originated within the ocean surrounding Rodinia and docked with Rodinia at -800 Ma. It does not contain Cadomian magmatism and consequently it is classified as an Avalonian extra-Cadomian terrane, The Lainici-Pfiius terrane is a Ganderian fragment strongly modified by Cadomian subduction-related magmatism, It is attached to the Moesia platform. The TisoviD terrane is an ophiolite that marks the boundary between Drfagsan and Lainici-Paius terranes. The other basement terranes of the Romanian Carpathians originated close to the Ordovician North- African orogen, as a result of the eastern Rheic Ocean opening and closure. Except for the Sebes-Lotru terrane that includes a lower metamorphic unit of Cadomian age, all the other terranes （Bretila, Tulghes, Negrisoara and Rebra in the East Carpathians, Somes, Biharia and Baia de Aries in the Apuseni mountains, Fagaras, Leaota, Carat and Pades in the South Carpathians） represent late Cambrian-Ordovician rock assemblages. Their provenance, is probably within paleo-nortbeast Africa, close to the Arabian-Nubian shield. The late Cambrian-Ordovician terranes are defined here as Carpathian-type terranes. According to their lithostratigraphy and origin, some are of continental margin magmatic arc setting, whereas others formed in rift and back-arc environment and closed to passive continental margin settings. In a paleo- geographic reconstruction, the continental margin magmatic arc terranes were first that drifted out, followed by the passive continental margin terranes with the back-arc terranes in their front. They accreted to Laurussia during the Variscan orogeny. Some of them （Sebes-Lotru in South Carpathians and Baia de Aries in Apuseni mountains） underwent eclogite-grade metamorphism. The Danubian terranes, the Bretila terrane and the Somes terrane were intruded by Variscan granitoids.
基金jointly supported by the Projects from China (Nos. U1701641, 41506050, 2016ZT06N331 and 2017M612794)
文摘Volcanic rocks in the Bangxi-Chenxing tectonic zone provide important carries for better understanding the Late Paleozoic tectonic evolution in Hainan and its temporal-spatial pattern of the eastern Paleotethyan evolution. This paper presents a set of new geochronological and geochemical data on the andesitic and dacitic rocks along the Bangxi-Chenxing tectonic zone in central Hainan. The rep- resentative andesitic and dacitic samples yield similar zircon U-Pb ages of 353^-3 and 351^-7 Ma, respec- tively, being of Early Carboniferous origin. These volcanic rocks are characterized by low TiO2 and high A1203 contents and are enriched in LILEs and LREEs but depletion in HFSEs, along with negative fNd（t） Values of =1.4-- -4.7 and high STSr/S6Sr（i） ratios of 0.707 2-0.710 1. Geochemical signatures suggest that the andesitic and dacitic samples might originate from a metasomatized wedge modified by the slab-derived component in a continental arc setting. In combination with the available data, it is pro- posed for the development of a Carboniferous continental arc in response to the eastern Paleotethyan evolution. The Bangxi-Chenxing tectonic zone might westerly link with the Jinshajiang-Ailaoshan-Song Ma suture zone, constituting an assemblage boundary between the South China and Indochina blocks.
基金Supported by the National Basic Research Program of China (Grant No. 2009CB825000)National Natural Science Foundation of China (Grant Nos. 40873043, 40821061, 90714010 and 40772042)+1 种基金Ministry of Education of China (Grant Nos. IRT0441, B07039 and NCET-06-0659)Foundation of the State Key Laboratory of Continental Dynamics, Northwest University
文摘The foramtion and evolution of collisional orogen is a prominent feature along convergent plate margins, and is generally a complex process. This article presents an integrated study of zircon genesis, U-Pb age and Lu-Hf isotope composition as well as geological characteristics for the western Dabie orogen to constrain its multi-stage evolution history. The results suggest that the formation of oceanic crust in the Huwan area was constrained at ca. 400―430 Ma, which was slightly later than the collision of the northern Qinling with the North China Block. It formed in a marginal basin in the northern margin of the Yangtze Block. The peak metamorphism of eclogite in the Huwan area occurred at ca. 310 Ma, and the timing of the initial exhumation of oceanic eclogite was about 270 Ma. The high to ultrahigh pressure (HP-UHP) metamorphic rocks in the Xinxian and the Hong'an metamorphic zones have the same ages and natures as those of the HP-UHP metamorphic rocks in the other Dabie-Sulu terrains, and also have experienced multi-stage exhumation, and thus can be taken as a coherent part of the Dabie-Sulu orogen. Therefore, the Qinling-Dabie-Sulu orogen is a typical multi-stage continental collision orogen, with an amalgamation process extending more than 200 Ma.
