鞍山东山风景区古老岩带呈巨型包体存在于立山奥长花岗岩(3.1Ga)中,其主体为条带状片麻岩(3.8Ga)。此外还有金云母透闪石岩、(含)黑云斜长角闪岩、闪长质片麻岩、变石英闪长质岩石、细粒奥长花岗岩、二长花岗岩、伟晶岩脉等。测定了部...鞍山东山风景区古老岩带呈巨型包体存在于立山奥长花岗岩(3.1Ga)中,其主体为条带状片麻岩(3.8Ga)。此外还有金云母透闪石岩、(含)黑云斜长角闪岩、闪长质片麻岩、变石英闪长质岩石、细粒奥长花岗岩、二长花岗岩、伟晶岩脉等。测定了部分岩石的锆石年龄,其中变石英闪长质岩石(A9604)为3.65Ga(Wan et al.,1999),闪长质片麻岩(A9317)为3.5Ga、二长花岗岩(类型Ⅰ,A9605)为3.1Ga、黑云斜长角闪岩(A0019)为3.3Ga、细粒奥长花岗岩(A0017)为3.2Ga、二长花岗岩(类型Ⅱ,A0020)为2.6Ga。有关岩石的地球化学组成特征在文中也进行了简要介绍。在此基础上,提出了该古老岩带的地质同位素年代演化序列,认为鞍山地区不同时代、不同成因地质体空间上共存是该区长期地质演化的结果,而不是后期构造作用把它们拼合到一起的。鞍山地区很可能存在>3.8Ga的古老地壳岩石。展开更多
Okinawa Trough is a back-arc, initial marginal sea basin, located behind the Ryukyu Arc-Trench System. The formation and evolution of the Okinawa Trough is intimately related to the subduction process of the Philippin...Okinawa Trough is a back-arc, initial marginal sea basin, located behind the Ryukyu Arc-Trench System. The formation and evolution of the Okinawa Trough is intimately related to the subduction process of the Philippine Sea Plate beneath the Eurasian Plate since the late Miocene. The tectonic evolution of the trough is similar to other active back-arcs, such as the Mariana Trough and southern Lau Basin, all of which are experiencing the initial rifting and subsequent spreading process. This study reviews all petrologic and geochemical data of mafic volcanic lavas from the Okinawa Trough, Ryukyu Arc, and Philippine Sea Plate, combined with geophysical data to indicate the relationship between the subduction sources （input） and arc or back-arc magmas （output） in the Philippine Sea Plate-Ryukyu Arc-Okinawa Trough system （PROS）. The results obtained showed that several components were variably involved in the petrogenesis of the Oki-nawa Trough lavas：sub-continental lithospheric mantle underlying the Eurasian Plate, Indian mid-oceanic ridge basalt （MORB）-type mantle, and Pacific MORB-type mantle. The addition of shallow aqueous fluids and deep hydrous melts from subducted components with the characteristics of Indian MORB-type mantle into the mantle source of lavas variably modifies the primitive mantle wedge beneath the Ryukyu and sub-continental lithospheric mantle （SCLM） beneath the Okinawa Trough. In the northeastern end of the trough and arc, instead of Indian MORB-type mantle, Pacific MORB-type mantle dominates the magma source. Along the strike of the Ryukyu Arc and Okinawa Trough, the systematic variations in trace element ratios and isotopic compositions reflect the first-order effect of variable subduction input on the magma source. In general, petrologic data, combined with geophysical data, imply that the Okinawa Trough is experiencing the＂seafloor spreading＂process in the southwest segment,＂rift propagation＂process in the middle seg-ment, and＂crustal extension＂process in 展开更多
Geochemical comparison of two suites of Cenozoic potassic volcanic rocks in western Yunnan reveals the existence of two mantle domains beneath this region, which corre- spond to their respective tectonic affinity. The...Geochemical comparison of two suites of Cenozoic potassic volcanic rocks in western Yunnan reveals the existence of two mantle domains beneath this region, which corre- spond to their respective tectonic affinity. The Erhai ultrapotassic rocks (42—24Ma) in western Yangtze Craton are characterized by LILE enrichment, HFSE depletion, low TiO2 content (<1%), high initial Sr/86Sr (0.7064—0.7094) and negative εNd (?3.84—?4.64). Geochemically similar to 87 K-rich volcanism in subduction setting, they were probably originated from a refractory spinel harzburgitic source metasomatized by subduction-related fluids. In contrast, the Maguan potas- sic magmas (<16Ma) in the South China Block show an OIB-type trace elemental signature, high TiO2 content (>2%), low initial 87 Sr/86Sr (0.7041—0.7060) and positive εNd (5.46—7.03). These features resemble the typical intraplate potassic rocks around the world. These rocks are thus interpreted as melting products of a fertile garnet lherzolitic source which has been infiltrated by small-volume, asthenosphere-derived silicate melts. The temporal and spatial distribution of these two types of K-rich rocks cannot be explained by any unified tectonic model. It is proposed that the Oligocene magmatism in the Erhai area may have resulted from convective thinning of the thickened lithosphere, whereas the post-Miocene volcanism in the Maguan area was related to the opening of South China Sea.展开更多
文摘鞍山东山风景区古老岩带呈巨型包体存在于立山奥长花岗岩(3.1Ga)中,其主体为条带状片麻岩(3.8Ga)。此外还有金云母透闪石岩、(含)黑云斜长角闪岩、闪长质片麻岩、变石英闪长质岩石、细粒奥长花岗岩、二长花岗岩、伟晶岩脉等。测定了部分岩石的锆石年龄,其中变石英闪长质岩石(A9604)为3.65Ga(Wan et al.,1999),闪长质片麻岩(A9317)为3.5Ga、二长花岗岩(类型Ⅰ,A9605)为3.1Ga、黑云斜长角闪岩(A0019)为3.3Ga、细粒奥长花岗岩(A0017)为3.2Ga、二长花岗岩(类型Ⅱ,A0020)为2.6Ga。有关岩石的地球化学组成特征在文中也进行了简要介绍。在此基础上,提出了该古老岩带的地质同位素年代演化序列,认为鞍山地区不同时代、不同成因地质体空间上共存是该区长期地质演化的结果,而不是后期构造作用把它们拼合到一起的。鞍山地区很可能存在>3.8Ga的古老地壳岩石。
基金The National Natural Science Foundation of China under contract Nos 41322036,41230960,40906034,41276003 and 41176058China Ocean Mineral Resources R&D Association(COMRA)under contract No.DY125-12-R-05
文摘Okinawa Trough is a back-arc, initial marginal sea basin, located behind the Ryukyu Arc-Trench System. The formation and evolution of the Okinawa Trough is intimately related to the subduction process of the Philippine Sea Plate beneath the Eurasian Plate since the late Miocene. The tectonic evolution of the trough is similar to other active back-arcs, such as the Mariana Trough and southern Lau Basin, all of which are experiencing the initial rifting and subsequent spreading process. This study reviews all petrologic and geochemical data of mafic volcanic lavas from the Okinawa Trough, Ryukyu Arc, and Philippine Sea Plate, combined with geophysical data to indicate the relationship between the subduction sources （input） and arc or back-arc magmas （output） in the Philippine Sea Plate-Ryukyu Arc-Okinawa Trough system （PROS）. The results obtained showed that several components were variably involved in the petrogenesis of the Oki-nawa Trough lavas：sub-continental lithospheric mantle underlying the Eurasian Plate, Indian mid-oceanic ridge basalt （MORB）-type mantle, and Pacific MORB-type mantle. The addition of shallow aqueous fluids and deep hydrous melts from subducted components with the characteristics of Indian MORB-type mantle into the mantle source of lavas variably modifies the primitive mantle wedge beneath the Ryukyu and sub-continental lithospheric mantle （SCLM） beneath the Okinawa Trough. In the northeastern end of the trough and arc, instead of Indian MORB-type mantle, Pacific MORB-type mantle dominates the magma source. Along the strike of the Ryukyu Arc and Okinawa Trough, the systematic variations in trace element ratios and isotopic compositions reflect the first-order effect of variable subduction input on the magma source. In general, petrologic data, combined with geophysical data, imply that the Okinawa Trough is experiencing the＂seafloor spreading＂process in the southwest segment,＂rift propagation＂process in the middle seg-ment, and＂crustal extension＂process in
基金supported by the National Natural Science Foundation of China(Grant No.49925308)the Chinese Academy of Sciences(Gramt Nos.KZCX2-SW-117,KZCX2-101 and KZCX2-209).
文摘Geochemical comparison of two suites of Cenozoic potassic volcanic rocks in western Yunnan reveals the existence of two mantle domains beneath this region, which corre- spond to their respective tectonic affinity. The Erhai ultrapotassic rocks (42—24Ma) in western Yangtze Craton are characterized by LILE enrichment, HFSE depletion, low TiO2 content (<1%), high initial Sr/86Sr (0.7064—0.7094) and negative εNd (?3.84—?4.64). Geochemically similar to 87 K-rich volcanism in subduction setting, they were probably originated from a refractory spinel harzburgitic source metasomatized by subduction-related fluids. In contrast, the Maguan potas- sic magmas (<16Ma) in the South China Block show an OIB-type trace elemental signature, high TiO2 content (>2%), low initial 87 Sr/86Sr (0.7041—0.7060) and positive εNd (5.46—7.03). These features resemble the typical intraplate potassic rocks around the world. These rocks are thus interpreted as melting products of a fertile garnet lherzolitic source which has been infiltrated by small-volume, asthenosphere-derived silicate melts. The temporal and spatial distribution of these two types of K-rich rocks cannot be explained by any unified tectonic model. It is proposed that the Oligocene magmatism in the Erhai area may have resulted from convective thinning of the thickened lithosphere, whereas the post-Miocene volcanism in the Maguan area was related to the opening of South China Sea.
