There are four deposit types related to a Permian mafic complex in northern Xinjiang, i.e., copper-nickel sulfide deposit, vanadic titanomagnetite deposit, magnetite （-cobalt） deposit and Cu-Ni- VTiFe composite depo...There are four deposit types related to a Permian mafic complex in northern Xinjiang, i.e., copper-nickel sulfide deposit, vanadic titanomagnetite deposit, magnetite （-cobalt） deposit and Cu-Ni- VTiFe composite deposit. The deposits are distributed spanning tectonic units with close and consecutive metallogenic ages. A transitional deposit type can occur among the end-member deposits. Trace elements of host rocks show that they can derive from similar source area. Hence, they constitute a particular metallogenic series related to a mafic-ultramafic complex that is also a symbol series of the post-collisional stage of the Central Asia Metallogenic Province （CAMP）. The metallogenic ages of the series are between 260 Ma and 300 Ma throughout the Permian. Unlike mineralization from a mantle plume, the metallogenic period of this series spans at least 40 Ma. Compared with related deposits of the Emeishan mantle plume, the North Xinjiang series has a similar ore-forming element assemblage but has preferably developed Cu-Ni sulfide deposits rather than vanadic titanomagnetite deposits. In concomitance with this series, North Xinjiang area has developed a set of syntectonic Au-Cu-Mo metallogenic series related to a felsic volcanic-intrusive complex, which might indicate that there is no direct relationship with mantle plume activity. From early to late, i.e., the sequence of copper-nickel sulfide to magnetite （-cobalt） to vanadic titanomagnetite deposit, the host rock series evolves from mafic-ultramafic and tholeiite series to mafic and alkalic series, the ~REE content tends to increase with increasing of REE fractionation, and some of the trace elements （particularly LIL） also show an increasing tendency. The above evolutionary regularity possibly reflects a course where the magma source deepens and thermal interface moves down, energy gradually exhausts, and neo-continental crust forming in the postcollision stage tends to stabilize.展开更多
The Beishan area has more than seventy mafic-ultramafic complexes sparsely distributed in the area and is of a big potential in mineral resources related to mafic-ultramafic intrusions. Many mafic-ultramafic intrusion...The Beishan area has more than seventy mafic-ultramafic complexes sparsely distributed in the area and is of a big potential in mineral resources related to mafic-ultramafic intrusions. Many mafic-ultramafic intrusions which are mostly in small sizes have been omitted by previous works. This research takes Huitongshan as the study area, which is a major district for mafic-ultramafic occurrences in Beishan. Advanced spaceborne thermal emission and reflection radiometer（ASTER） data have been processed and interpreted for mapping the mafic-ultramafic complex. ASTER data were processed by different techniques that were selected based on image reflectance and laboratory emissivity spectra. The visible near-infrared（VNIR） and short wave infrared（SWIR） data were transformed using band ratios and minimum noise fraction（MNF）, while the thermal infrared（TIR） data were processed using mafic index（MI） and principal components analysis（PCA）. ASTER band ratios（6/8, 5/4, 2/1） in RGB image and MNF（1, 2, 4） in RGB image were powerful in distinguishing the subtle differences between the various rock units. PCA applied to all five bands of ASTER TIR imagery highlighted marked differences among the mafic rock units and was more effective than the MI in differentiating mafic-ultramafic rocks. Our results were consistent with information derived from local geological maps. Based on the remote sensing results and field inspection, eleven gabbroic intrusions and a pyroxenite occurrence were recognized for the first time. A new geologic map of the Huitongshan area was created by integrating the results of remote sensing, previous geological maps and field inspection. It is concluded that the workflow of ASTER image processing, interpretation and ground inspection has great potential for mafic-ultramafic rocks identifying and relevant mineral targeting in the sparsely vegetated arid region of northwestern China.展开更多
Early Permian mafic-ultramafic complexes in eastern Xinjiang （新疆） are mainly distributed in the Beishan （北山） area, Mid-Tianshan （天山） massif and Jueluotage （觉罗塔塔） belt. Systematic compositional mappin...Early Permian mafic-ultramafic complexes in eastern Xinjiang （新疆） are mainly distributed in the Beishan （北山） area, Mid-Tianshan （天山） massif and Jueluotage （觉罗塔塔） belt. Systematic compositional mapping of olivines from these Early Permian mafic-ultramafic complexes demonstrates that an apparently spatial distribution and heterogeneous partial melting in the mantle source exists from the Beishan area, across the Mid-Tianshan massif, to the Jueluotage belt from the south to the north. This is probably consistent with the spatial evolutional differences and tectonic features of these three belts. The decreasing degree of partial melting, as revealed by decreasing Fo contents of olivines, from south to north and from east to west reflects the southward subduction of the Paleo-Asian Ocean and the south location of the indistinct mantle plume in the Permian. Simultan ously, NiO and Fo-mapping in olivine also indicates that sulfide segregation before olivine crystallization played an important role in Ni-Cu mineralization in the mafic-ultramafic complexes. Olivines with the compositional range of Fo （77-86） and NiO （less than 0.22 wt.%） are more favorable for Ni-Cu sulfide mineralization.展开更多
There is a general consensus that most ophiolites formed above subduction zones(Pearce,2003),particularly during forearc extension at subduction initiation(Shervais,2001;Stern,2004;Whattam and Stern,2011).'Supra-S...There is a general consensus that most ophiolites formed above subduction zones(Pearce,2003),particularly during forearc extension at subduction initiation(Shervais,2001;Stern,2004;Whattam and Stern,2011).'Supra-Subduction zone'(SSZ)ophiolites such as the well-studied Tethyan ophiolites,generally display a characteristic sequential evolution from mid-oceanic ridge basalts(MORBs)to island arc tholeiities(IATs)or bonites(BONs)(Pearce,2003;Dilek and Furnes,2009,2011),which were generated in sequence from the decompression melting of asthenospheric mantle and partial melting of subduction-metasomatized depleted mantle(Stern and Bloomer,1992;Dilek and Furnes,2009;Whattam and Stern,2011).However,ophiolites with MORB and/or oceanic-island basalt(OIB)affinities are rare,and their origin and tectonic nature are poorly understood(Boedo et al.,2013;Saccani et al.,2013).It is interesting that the composition of these ophiolites from the central Tibetan Plateau(CTP)is dominated by MORBs and minor OIBs and a distinct lack of IATs and BONs,which is inconsistent with most ophiolites worldwide(Robinson and Zhou,2008;Zhang et al.,2008).But the generation and tectonic nature of these ophiolites are still controversial.*In this study,we present new geochronological,mineralogical and Sr-Nd isotopic data for the Chayong and Xiewu mafic complexes in the western Garzê-Litang suture zone(GLS),a typical Paleo-Tethyan suture crossing the CTP(Fig.1).The Triassic ophiolite in the western GLS has been described by Li et al.(2009),who foundthat it mainly consists of gabbros,diabases,pillow basalts and a few metamorphic peridotites.The ophiolite has been tectonically dismembered and crops out in Triassic clastic rocks and limestones as tectonic blocks.The Chayong and Xiewu mafic complexes are generally regarded as important fragments of the Triassic ophiolites(e.g.,Jin,2006;Li et al.,2009).Zircon LA-ICP-MS U-Pb ages of234±3 Ma and 236±2 Ma can be interpreted as formation times of the Chayong and Xiewu mafic complexes,respectively.The basalts and gabbros of the Chayong complexexhibitenrichedMORB(E-MORB)compositional affinities except for a weak depletion of Nb,Ta and Ti relative to the primitive mantle,whereas the basalts and gabbros of the Xiewu complex display distinct E-MORB and OIB affinities.The geochemical features suggest a probable fractionation of olivine±clinopyroxene±plagioclase as well as insignificant crustal contamination.The geochemical and Sr-Nd isotopic data reveal that the Chayong mafic rocks may have been derived from depleted MORB-type mantle metasomatized by crustal components and Xiewu mafic rocks from enriched lithosphericmantlemetasomatizedbyOIB-like components.The ratios of Zn/Fet,La/Yb and Sm/Yb indicate that these mafic melts were produced by the partial melting of garnet+minor spinel-bearing peridotite or spinel±minor garnet-bearing peridotite.We propose thatback-arcbasinspreadingassociated with OIB/seamount recycling had occurred in the western GLS at least since the Middle Triassic times,and the decompression melting of the depleted MORB-type asthenospheremantleandpartialmeltingof sub-continental lithosphere were metasomatized by plume-related melts,such as OIBs,which led to the generation of the Chayong and Xiewu mafic melts.展开更多
More than twenty mafic-ultramafic complexes. which host several medium-or large-sized Cu-Ni deposits, occur along the Huangshan-Jingerquan (HJ ) belt in EastXinjiang. Rock types in these complexes are predominated by ...More than twenty mafic-ultramafic complexes. which host several medium-or large-sized Cu-Ni deposits, occur along the Huangshan-Jingerquan (HJ ) belt in EastXinjiang. Rock types in these complexes are predominated by peridotite, pyroxene peri-dotite, olivine pyroxenite, gabbronorite, orthopyroxene gabbro, troctolite, gabbro anddiorite. The ultramafic rocks are relatively Fe-euriched and are characterised by an as-semblage of olivine + orthopyroxene + clinopyroxene + hornblend ±plagioclase withoutobvious metamorphic textures. Chemically these complexes are relatively Fe-enrichedand show a tholeiitic trend of evolution. The complexes in this belt are intruded underthe extensional environment in a Mid-Carboniferous back-arc basin. They call be consid-ered as a new type of mafic-ultramafic complexes in orogenic belts, as designated by thename of the East-Xinjiang-type complexes.展开更多
Numeral Permian mafic-ultramafic complexes occur in the Beishan terrane atthe northeastern margin of the Tarim craton,southwestern Central Asian Orogenic Belt,including the Pobei,Cantoushan,Bijiashan,Hongshishan,Xuanw...Numeral Permian mafic-ultramafic complexes occur in the Beishan terrane atthe northeastern margin of the Tarim craton,southwestern Central Asian Orogenic Belt,including the Pobei,Cantoushan,Bijiashan,Hongshishan,Xuanwoling,Zhongposhan and Luodong etc.,intrusions(Qin et al.,2011;Zhang et al.,2017;Xue et al.,2018).These Beishan mafic-ultramafic complexes are composed of peridotite,pyroxenite.展开更多
The mafic enclaves from Paleoproterozoic domain are considered to be the results of large-scale crust-mantle interaction and magma mixing. In this paper, petrography, mineralogy and geochemistry were jointly used to d...The mafic enclaves from Paleoproterozoic domain are considered to be the results of large-scale crust-mantle interaction and magma mixing. In this paper, petrography, mineralogy and geochemistry were jointly used to determine the origin of the mafic enclaves and their relationship with the host granitoids of the Kan granite-gneiss complex. This study also provides new information on crust-mantle interactions. The mafic enclaves of the Kan vary in shape and size and have intermediate chemical compositions. The diagrams used show a number of similarities in the major elements (and often in the trace elements) between the mafic enclaves and the host granitoids. Geochemical show that the Kan rock are metaluminous, enriched in silica, medium to high-K calc-alkaline I-type granite. The similarities reflect a mixing of basic and acid magma. Mafic enclaves have a typical magmatic structure, which is characterized by magma mixing. The genesis of these rocks is associated with the context of subduction. They result from the mixing of a mafic magma originating from the mantle and linked to subduction, and a granitic magma (type I granite) that arises from the partial melting of the crust.展开更多
The SHRIMP zircon U-Pb dating was carried out and yielded 287±5 Ma (MSWD = 0.34) and 274±3 Ma (MSWD = 1.35) for the Kalatongke No. 1 and Huangshan- dong Cu-Ni-bearing mafic-ultramafic complexes. These ages a...The SHRIMP zircon U-Pb dating was carried out and yielded 287±5 Ma (MSWD = 0.34) and 274±3 Ma (MSWD = 1.35) for the Kalatongke No. 1 and Huangshan- dong Cu-Ni-bearing mafic-ultramafic complexes. These ages are much more precise than pre-existing rock-mineral Rb-Sr, Sm-Nd and Re-Os isochron ages for the two complexes and constrain the timing of not only the complexes but also the magmatic Cu-Ni sulfide deposits more reliably. It is neces- sary to carefully reevaluate the previous chronological data for the complexes. The Cu-Ni-bearing mafic-ultramafic com- plexes have the ages similar to those of postcollisional A-type granites in the same area, implying that they could be related to the delamination of lithospheric mantle and upwelling and partial melting of asthenospheric mantle in postcollisional setting. Therefore, the Cu-Ni-bearing mafic-ultramafic com- plexes are a direct indicator of vertical growth of the conti- nental crustal in the Central Asian Orogenic Belt.展开更多
Objective Petrogenesis of the Paleoproterozoic mafic dikes and their tectonic implications are of great significance to the tectonic evolution of the Yangtze craton as well as the paleoposition of the Yangtze craton r...Objective Petrogenesis of the Paleoproterozoic mafic dikes and their tectonic implications are of great significance to the tectonic evolution of the Yangtze craton as well as the paleoposition of the Yangtze craton relative to the Columbia supercontinent.Till now,展开更多
Neoarchean metamorphic mafic rocks in the lower and the middle Wutai Complex mainly comprise metamorphic gabbros, amphibolites and chlorite schists. They can be subdivided into three groups according to chondrite norm...Neoarchean metamorphic mafic rocks in the lower and the middle Wutai Complex mainly comprise metamorphic gabbros, amphibolites and chlorite schists. They can be subdivided into three groups according to chondrite normalized REE patterns. Rocks in Group #1 are characterized by nearly flat REE patterns （Lan/Ybn=0.86-1.3）, the lowest total REEs （29-52 ppm）, and weak negative to positive Eu anomalies （Eun/Eun=0.84-1.02）, nearly flat primitive mantle normalized patterns and strong negative Zr（Hf） anomalies. Their geochemical characteristics in REEs and trace elements are similar to those of ocean plateau tholeiite, which imply that this group of rocks can represent remnants of Archean oceanic crust derived from a mantle plume. Rocks in Group #2 are characterized by moderate total REEs （34-116 ppm）, LREE-enriched （Lan/Ybn=1.76-4.34） chondrite normalized REE patterns with weak Eu anomalies （Eun/Eun=0.76-1.16）, and negative Nb, Ta, Zr（Hf）, Ti anomalies in the primitive mantle normalized spider diagram. The REE and trace element characteristics indicate that they represent arc magmas originating from a sub-arc mantle wedge metasomatized by slab-derived fluids. Rocks in Group #3 are characterized by the highest total REEs （61-192 ppm）, the strongest LREEs enrichment （Lan/Ybn=7.12-16） with slightly negative Eu anomalies （Eun/Eun=0.81-0.95） in the chondrite normalized diagram. In the primitive mantle normalized diagram, these rocks are characterized by large negative anomalies in Nb, Ta, Ti, negative to no Zr anomalies. They represent arc magmas originating from a sub-arc mantle wedge enriched in slab-derived melts. The three groups of rocks imply that the formation of the Neoarchean Wutai Complex is related to mantle plumes and island-arc interaction.展开更多
The Yushugou HP granulite-peridotite complex is located at east of northern margin of southern Tianshan mountains,China,which consists of granulite unit and peridotite unit mainly.Because of the rare association of
The Singhbhum craton of the eastern Indian shield consists of two major crustal provinces viz.,Chotanagpur Gneissic Complex(CGC)and Singhbhum Granite Complex;separated by a Singhbhum Mobile Belt.There
The research on dyke swarms is very important,for it can not only shed light on within-plate geological processes of some regions but also contribute to our understanding on evolution of a specific orogenic belt.The Y...The research on dyke swarms is very important,for it can not only shed light on within-plate geological processes of some regions but also contribute to our understanding on evolution of a specific orogenic belt.The Yangtze Block,展开更多
The Singhbhum craton of the eastern India consists of the Singhbhum Granite Complex(SGC)and the Chotanagpur Gneissic Complex(CGC)separated by the Singhbhum Mobile Belt(SMB).The CGC is intruded by Mesoproterozoic as we...The Singhbhum craton of the eastern India consists of the Singhbhum Granite Complex(SGC)and the Chotanagpur Gneissic Complex(CGC)separated by the Singhbhum Mobile Belt(SMB).The CGC is intruded by Mesoproterozoic as well as Cretaceous mafic dykes;in展开更多
Mineral chemistry, whole-rock major oxide, and trace element compositions have been determined for the Tuerkubantao mafic-ultramafic intrusion, in order to understand the early Paleozoic tectonic evolution of the West...Mineral chemistry, whole-rock major oxide, and trace element compositions have been determined for the Tuerkubantao mafic-ultramafic intrusion, in order to understand the early Paleozoic tectonic evolution of the West Junggar orogenic belt at the southern margin of the Central Asian orogenic belt. The Tuerkubantao mafic-ultramafic intrusion is a well-differentiated complex comprising peridotite, olivine pyroxenite, gabbro, and diorite. The ultramafic rocks are mostly seen in the central part of the intrusion and surrounded by mafic rocks. The Tuerkubantao intrusive rocks are characterized by enrichment of large ion lithophile elements and depleted high field strength elements relative to N-MORB. In addition, the Tuerkubantao intrusion displays relatively low Th/U and Nb/U （1.13-2.98 and 2.53-7.02, respectively） and high La/Nb and Ba/Nb （1.15 4.19 and 37.7-79.82, respectively）. These features indicate that the primary magma of the intrusion was derived from partial melting of a previously metasomatized mantle source in a subduction setting. The trace element patterns of peridotites, gabbros, and diorite in the Tuerkubantao intrusion have sub-parallel trends, suggesting that the different rock types are related to each other by differentiation of the same primary magma. The intrusive contact between peridotite and gabbro clearly suggest that the Tuerkubantao is not a fragment of an ophiolite. However, the Tuerkubantao intrusion displays many similarities with Alaskan-type mafic-ultramafic intrusions along major sutures of Phanerozoic orogenic belts. Common features include their geodynamic setting, internal lithological zoning, and geochemistry. The striking similarities indicate that the middle Devonian Tuerkubantao intrusion likely formed in a subduction-related setting similar to that of the Alaskan-type intrusions. In combination with the Devonian magmatism and porphyry mineralization, we propose that subduction of the oceanic slab has widely existed in the expansive oceans during the Devonian around the Junggar block.展开更多
文摘There are four deposit types related to a Permian mafic complex in northern Xinjiang, i.e., copper-nickel sulfide deposit, vanadic titanomagnetite deposit, magnetite （-cobalt） deposit and Cu-Ni- VTiFe composite deposit. The deposits are distributed spanning tectonic units with close and consecutive metallogenic ages. A transitional deposit type can occur among the end-member deposits. Trace elements of host rocks show that they can derive from similar source area. Hence, they constitute a particular metallogenic series related to a mafic-ultramafic complex that is also a symbol series of the post-collisional stage of the Central Asia Metallogenic Province （CAMP）. The metallogenic ages of the series are between 260 Ma and 300 Ma throughout the Permian. Unlike mineralization from a mantle plume, the metallogenic period of this series spans at least 40 Ma. Compared with related deposits of the Emeishan mantle plume, the North Xinjiang series has a similar ore-forming element assemblage but has preferably developed Cu-Ni sulfide deposits rather than vanadic titanomagnetite deposits. In concomitance with this series, North Xinjiang area has developed a set of syntectonic Au-Cu-Mo metallogenic series related to a felsic volcanic-intrusive complex, which might indicate that there is no direct relationship with mantle plume activity. From early to late, i.e., the sequence of copper-nickel sulfide to magnetite （-cobalt） to vanadic titanomagnetite deposit, the host rock series evolves from mafic-ultramafic and tholeiite series to mafic and alkalic series, the ~REE content tends to increase with increasing of REE fractionation, and some of the trace elements （particularly LIL） also show an increasing tendency. The above evolutionary regularity possibly reflects a course where the magma source deepens and thermal interface moves down, energy gradually exhausts, and neo-continental crust forming in the postcollision stage tends to stabilize.
基金supported by the Special Fund for Basic Scientific Research of Central Colleges (Nos. 2014G1271060, 2013G1271103)Chang’an University, China and the High Resolution Earth Observation Systems of National Science and Technology Major Projects
文摘The Beishan area has more than seventy mafic-ultramafic complexes sparsely distributed in the area and is of a big potential in mineral resources related to mafic-ultramafic intrusions. Many mafic-ultramafic intrusions which are mostly in small sizes have been omitted by previous works. This research takes Huitongshan as the study area, which is a major district for mafic-ultramafic occurrences in Beishan. Advanced spaceborne thermal emission and reflection radiometer（ASTER） data have been processed and interpreted for mapping the mafic-ultramafic complex. ASTER data were processed by different techniques that were selected based on image reflectance and laboratory emissivity spectra. The visible near-infrared（VNIR） and short wave infrared（SWIR） data were transformed using band ratios and minimum noise fraction（MNF）, while the thermal infrared（TIR） data were processed using mafic index（MI） and principal components analysis（PCA）. ASTER band ratios（6/8, 5/4, 2/1） in RGB image and MNF（1, 2, 4） in RGB image were powerful in distinguishing the subtle differences between the various rock units. PCA applied to all five bands of ASTER TIR imagery highlighted marked differences among the mafic rock units and was more effective than the MI in differentiating mafic-ultramafic rocks. Our results were consistent with information derived from local geological maps. Based on the remote sensing results and field inspection, eleven gabbroic intrusions and a pyroxenite occurrence were recognized for the first time. A new geologic map of the Huitongshan area was created by integrating the results of remote sensing, previous geological maps and field inspection. It is concluded that the workflow of ASTER image processing, interpretation and ground inspection has great potential for mafic-ultramafic rocks identifying and relevant mineral targeting in the sparsely vegetated arid region of northwestern China.
基金supported by the National Natural Science Foundation of China (Nos. 41030424,41173011)the Knowledge Innovation Program of the Chinese Academy of Sciences (No. KZCX2-YW-107)the China Postdoctoral Science Foundation to Benxun Su
文摘Early Permian mafic-ultramafic complexes in eastern Xinjiang （新疆） are mainly distributed in the Beishan （北山） area, Mid-Tianshan （天山） massif and Jueluotage （觉罗塔塔） belt. Systematic compositional mapping of olivines from these Early Permian mafic-ultramafic complexes demonstrates that an apparently spatial distribution and heterogeneous partial melting in the mantle source exists from the Beishan area, across the Mid-Tianshan massif, to the Jueluotage belt from the south to the north. This is probably consistent with the spatial evolutional differences and tectonic features of these three belts. The decreasing degree of partial melting, as revealed by decreasing Fo contents of olivines, from south to north and from east to west reflects the southward subduction of the Paleo-Asian Ocean and the south location of the indistinct mantle plume in the Permian. Simultan ously, NiO and Fo-mapping in olivine also indicates that sulfide segregation before olivine crystallization played an important role in Ni-Cu mineralization in the mafic-ultramafic complexes. Olivines with the compositional range of Fo （77-86） and NiO （less than 0.22 wt.%） are more favorable for Ni-Cu sulfide mineralization.
基金financially supported by the National Nature Science Foundation of China (Grant 41272079)
文摘There is a general consensus that most ophiolites formed above subduction zones(Pearce,2003),particularly during forearc extension at subduction initiation(Shervais,2001;Stern,2004;Whattam and Stern,2011).'Supra-Subduction zone'(SSZ)ophiolites such as the well-studied Tethyan ophiolites,generally display a characteristic sequential evolution from mid-oceanic ridge basalts(MORBs)to island arc tholeiities(IATs)or bonites(BONs)(Pearce,2003;Dilek and Furnes,2009,2011),which were generated in sequence from the decompression melting of asthenospheric mantle and partial melting of subduction-metasomatized depleted mantle(Stern and Bloomer,1992;Dilek and Furnes,2009;Whattam and Stern,2011).However,ophiolites with MORB and/or oceanic-island basalt(OIB)affinities are rare,and their origin and tectonic nature are poorly understood(Boedo et al.,2013;Saccani et al.,2013).It is interesting that the composition of these ophiolites from the central Tibetan Plateau(CTP)is dominated by MORBs and minor OIBs and a distinct lack of IATs and BONs,which is inconsistent with most ophiolites worldwide(Robinson and Zhou,2008;Zhang et al.,2008).But the generation and tectonic nature of these ophiolites are still controversial.*In this study,we present new geochronological,mineralogical and Sr-Nd isotopic data for the Chayong and Xiewu mafic complexes in the western Garzê-Litang suture zone(GLS),a typical Paleo-Tethyan suture crossing the CTP(Fig.1).The Triassic ophiolite in the western GLS has been described by Li et al.(2009),who foundthat it mainly consists of gabbros,diabases,pillow basalts and a few metamorphic peridotites.The ophiolite has been tectonically dismembered and crops out in Triassic clastic rocks and limestones as tectonic blocks.The Chayong and Xiewu mafic complexes are generally regarded as important fragments of the Triassic ophiolites(e.g.,Jin,2006;Li et al.,2009).Zircon LA-ICP-MS U-Pb ages of234±3 Ma and 236±2 Ma can be interpreted as formation times of the Chayong and Xiewu mafic complexes,respectively.The basalts and gabbros of the Chayong complexexhibitenrichedMORB(E-MORB)compositional affinities except for a weak depletion of Nb,Ta and Ti relative to the primitive mantle,whereas the basalts and gabbros of the Xiewu complex display distinct E-MORB and OIB affinities.The geochemical features suggest a probable fractionation of olivine±clinopyroxene±plagioclase as well as insignificant crustal contamination.The geochemical and Sr-Nd isotopic data reveal that the Chayong mafic rocks may have been derived from depleted MORB-type mantle metasomatized by crustal components and Xiewu mafic rocks from enriched lithosphericmantlemetasomatizedbyOIB-like components.The ratios of Zn/Fet,La/Yb and Sm/Yb indicate that these mafic melts were produced by the partial melting of garnet+minor spinel-bearing peridotite or spinel±minor garnet-bearing peridotite.We propose thatback-arcbasinspreadingassociated with OIB/seamount recycling had occurred in the western GLS at least since the Middle Triassic times,and the decompression melting of the depleted MORB-type asthenospheremantleandpartialmeltingof sub-continental lithosphere were metasomatized by plume-related melts,such as OIBs,which led to the generation of the Chayong and Xiewu mafic melts.
文摘More than twenty mafic-ultramafic complexes. which host several medium-or large-sized Cu-Ni deposits, occur along the Huangshan-Jingerquan (HJ ) belt in EastXinjiang. Rock types in these complexes are predominated by peridotite, pyroxene peri-dotite, olivine pyroxenite, gabbronorite, orthopyroxene gabbro, troctolite, gabbro anddiorite. The ultramafic rocks are relatively Fe-euriched and are characterised by an as-semblage of olivine + orthopyroxene + clinopyroxene + hornblend ±plagioclase withoutobvious metamorphic textures. Chemically these complexes are relatively Fe-enrichedand show a tholeiitic trend of evolution. The complexes in this belt are intruded underthe extensional environment in a Mid-Carboniferous back-arc basin. They call be consid-ered as a new type of mafic-ultramafic complexes in orogenic belts, as designated by thename of the East-Xinjiang-type complexes.
基金supported financially by the NSFC projects(Grant Nos.U1403291,41802074,41830216,41202044)projects of the China Geological Survey(Grant Nos.1212010811033,12120113096500,12120113094000,DD20160123,DD20160009 and DD20179607)+1 种基金the IGCP 662 projectDDE.
文摘Numeral Permian mafic-ultramafic complexes occur in the Beishan terrane atthe northeastern margin of the Tarim craton,southwestern Central Asian Orogenic Belt,including the Pobei,Cantoushan,Bijiashan,Hongshishan,Xuanwoling,Zhongposhan and Luodong etc.,intrusions(Qin et al.,2011;Zhang et al.,2017;Xue et al.,2018).These Beishan mafic-ultramafic complexes are composed of peridotite,pyroxenite.
文摘The mafic enclaves from Paleoproterozoic domain are considered to be the results of large-scale crust-mantle interaction and magma mixing. In this paper, petrography, mineralogy and geochemistry were jointly used to determine the origin of the mafic enclaves and their relationship with the host granitoids of the Kan granite-gneiss complex. This study also provides new information on crust-mantle interactions. The mafic enclaves of the Kan vary in shape and size and have intermediate chemical compositions. The diagrams used show a number of similarities in the major elements (and often in the trace elements) between the mafic enclaves and the host granitoids. Geochemical show that the Kan rock are metaluminous, enriched in silica, medium to high-K calc-alkaline I-type granite. The similarities reflect a mixing of basic and acid magma. Mafic enclaves have a typical magmatic structure, which is characterized by magma mixing. The genesis of these rocks is associated with the context of subduction. They result from the mixing of a mafic magma originating from the mantle and linked to subduction, and a granitic magma (type I granite) that arises from the partial melting of the crust.
文摘The SHRIMP zircon U-Pb dating was carried out and yielded 287±5 Ma (MSWD = 0.34) and 274±3 Ma (MSWD = 1.35) for the Kalatongke No. 1 and Huangshan- dong Cu-Ni-bearing mafic-ultramafic complexes. These ages are much more precise than pre-existing rock-mineral Rb-Sr, Sm-Nd and Re-Os isochron ages for the two complexes and constrain the timing of not only the complexes but also the magmatic Cu-Ni sulfide deposits more reliably. It is neces- sary to carefully reevaluate the previous chronological data for the complexes. The Cu-Ni-bearing mafic-ultramafic com- plexes have the ages similar to those of postcollisional A-type granites in the same area, implying that they could be related to the delamination of lithospheric mantle and upwelling and partial melting of asthenospheric mantle in postcollisional setting. Therefore, the Cu-Ni-bearing mafic-ultramafic com- plexes are a direct indicator of vertical growth of the conti- nental crustal in the Central Asian Orogenic Belt.
基金financially supported by National Science Foundation of China(grant No.41303026)the funded project of the China Geological Survey(grants No.DD20160030,DD20160351 and DD20160029)
文摘Objective Petrogenesis of the Paleoproterozoic mafic dikes and their tectonic implications are of great significance to the tectonic evolution of the Yangtze craton as well as the paleoposition of the Yangtze craton relative to the Columbia supercontinent.Till now,
基金The National Natural Science Foundation of. China （Grant No.40420120135 and 40472096） are thankefl for the fthancial support.
文摘Neoarchean metamorphic mafic rocks in the lower and the middle Wutai Complex mainly comprise metamorphic gabbros, amphibolites and chlorite schists. They can be subdivided into three groups according to chondrite normalized REE patterns. Rocks in Group #1 are characterized by nearly flat REE patterns （Lan/Ybn=0.86-1.3）, the lowest total REEs （29-52 ppm）, and weak negative to positive Eu anomalies （Eun/Eun=0.84-1.02）, nearly flat primitive mantle normalized patterns and strong negative Zr（Hf） anomalies. Their geochemical characteristics in REEs and trace elements are similar to those of ocean plateau tholeiite, which imply that this group of rocks can represent remnants of Archean oceanic crust derived from a mantle plume. Rocks in Group #2 are characterized by moderate total REEs （34-116 ppm）, LREE-enriched （Lan/Ybn=1.76-4.34） chondrite normalized REE patterns with weak Eu anomalies （Eun/Eun=0.76-1.16）, and negative Nb, Ta, Zr（Hf）, Ti anomalies in the primitive mantle normalized spider diagram. The REE and trace element characteristics indicate that they represent arc magmas originating from a sub-arc mantle wedge metasomatized by slab-derived fluids. Rocks in Group #3 are characterized by the highest total REEs （61-192 ppm）, the strongest LREEs enrichment （Lan/Ybn=7.12-16） with slightly negative Eu anomalies （Eun/Eun=0.81-0.95） in the chondrite normalized diagram. In the primitive mantle normalized diagram, these rocks are characterized by large negative anomalies in Nb, Ta, Ti, negative to no Zr anomalies. They represent arc magmas originating from a sub-arc mantle wedge enriched in slab-derived melts. The three groups of rocks imply that the formation of the Neoarchean Wutai Complex is related to mantle plumes and island-arc interaction.
文摘The Yushugou HP granulite-peridotite complex is located at east of northern margin of southern Tianshan mountains,China,which consists of granulite unit and peridotite unit mainly.Because of the rare association of
文摘The Singhbhum craton of the eastern Indian shield consists of two major crustal provinces viz.,Chotanagpur Gneissic Complex(CGC)and Singhbhum Granite Complex;separated by a Singhbhum Mobile Belt.There
文摘The research on dyke swarms is very important,for it can not only shed light on within-plate geological processes of some regions but also contribute to our understanding on evolution of a specific orogenic belt.The Yangtze Block,
文摘The Singhbhum craton of the eastern India consists of the Singhbhum Granite Complex(SGC)and the Chotanagpur Gneissic Complex(CGC)separated by the Singhbhum Mobile Belt(SMB).The CGC is intruded by Mesoproterozoic as well as Cretaceous mafic dykes;in
基金financially supported by the Chinese National Science and Technology Program during the 12th Five-year Plan Period(2011BAB06B01)the Program for New Century Excellent Talents in University(Grant No.NCET-10-0324)+2 种基金NSFC research grants(41303031,41172090,41040025)the Fundamental Research Funds for the Central Universities(2013bhzx0015)Open Funds from the State Key Laboratory of Ore Deposit Geochemistry,Institute of Geochemistry,Chinese Academy of Sciences(201102)
文摘Mineral chemistry, whole-rock major oxide, and trace element compositions have been determined for the Tuerkubantao mafic-ultramafic intrusion, in order to understand the early Paleozoic tectonic evolution of the West Junggar orogenic belt at the southern margin of the Central Asian orogenic belt. The Tuerkubantao mafic-ultramafic intrusion is a well-differentiated complex comprising peridotite, olivine pyroxenite, gabbro, and diorite. The ultramafic rocks are mostly seen in the central part of the intrusion and surrounded by mafic rocks. The Tuerkubantao intrusive rocks are characterized by enrichment of large ion lithophile elements and depleted high field strength elements relative to N-MORB. In addition, the Tuerkubantao intrusion displays relatively low Th/U and Nb/U （1.13-2.98 and 2.53-7.02, respectively） and high La/Nb and Ba/Nb （1.15 4.19 and 37.7-79.82, respectively）. These features indicate that the primary magma of the intrusion was derived from partial melting of a previously metasomatized mantle source in a subduction setting. The trace element patterns of peridotites, gabbros, and diorite in the Tuerkubantao intrusion have sub-parallel trends, suggesting that the different rock types are related to each other by differentiation of the same primary magma. The intrusive contact between peridotite and gabbro clearly suggest that the Tuerkubantao is not a fragment of an ophiolite. However, the Tuerkubantao intrusion displays many similarities with Alaskan-type mafic-ultramafic intrusions along major sutures of Phanerozoic orogenic belts. Common features include their geodynamic setting, internal lithological zoning, and geochemistry. The striking similarities indicate that the middle Devonian Tuerkubantao intrusion likely formed in a subduction-related setting similar to that of the Alaskan-type intrusions. In combination with the Devonian magmatism and porphyry mineralization, we propose that subduction of the oceanic slab has widely existed in the expansive oceans during the Devonian around the Junggar block.
