The major elements, trace elements. K-Ar age and Sr-Nd-Pb isotopie systems ofthe Cenozoic volcanic rocks in Daheishan Island and Cishan, Penglai, Shandong Province aremeasured. The volcanic rocks ( olivine-nephelinite...The major elements, trace elements. K-Ar age and Sr-Nd-Pb isotopie systems ofthe Cenozoic volcanic rocks in Daheishan Island and Cishan, Penglai, Shandong Province aremeasured. The volcanic rocks ( olivine-nephelinite and nephcline-basanite ) in Daheishan Islanderupted periodically in an interval of 0.32 Ma, from 8.72 Ma. 8.39 Ma. 8.08 Ma to 7.73 Ma. Thevolcanic rocks arc all rich in light REEs. They are similar to the OIB-type alkali basalt in thetrace elements normalized model by primordial mantle: rich in high field elements such as Nb and Ta,and imcompatible elements such as Cs. Rb, Ba, Th. U. The volcanic rocks show a depletion of K andRb elements. It is suggested by the trace elements that the olivine-nephelinite in Daheishan Islandis originated from deep resources under the continental mantle. ε Nd (0) values of the volcanicrocks in Daheishan Island and Cishan are 5.31～8.51 and 7.33 respectively, suggesting that thevolcanic rocks are from the depleted mantle resources, which have higher Sm/Nd ratios than the CHUR.^(143)Nd /^(144)Nd ratios ot Daheishan Island olivine-nephelinite and Cishan alkali basalts are0.512 910～0.513 074 and 0.513 014 respectively. The ^(87)Sr /^(86)Sr of Daheishan Island volcanicrocks are lower than that of Cishan, 0.703 427 ～0.703 482 and 0.703 895 respectively. The DaheishanIsland olivine-nephelinite has the Pb isotopie values as follows: ^(206)Pb/^(204)Pb= 18.028 9～17.972 8. ^(207)Pb / ^(204)Pb = 15.435 8 ～15.402 2 and ^(208)Pb /^(204)Pb = 38.087 6～37.997 5.lower than those of Cishan basanite. The Cishan basanite has ^(206)Pb/^(204)Pb= 18.240 1. ^(207)Pb/^(204)Pb= 15.564 5 and ^(208)Pb /^(204)Pb = 38.535. The authors suggest that theolivine-nephelinite in Daheishan Island is similar to the E-type MORB or Hawaii OIB, and the alkalibasalts in Cishan similar to the Kerguelen OIB. The dominant mantle components of DM+PREMA andperhaps DM ( Dupal type ) are the dominant mantle components for volcanic rocks in Daheishan Islandand Cishan. The PREMA component plays an important role.展开更多
The Nadingcuo volcanic rock suite is the most volmninous Cenozoic volcanic suite in the southern Qiangtang area of the northern Tibetan Plateau. These high-K calc-alkaline volcanic rocks were formed between 36 and 34 ...The Nadingcuo volcanic rock suite is the most volmninous Cenozoic volcanic suite in the southern Qiangtang area of the northern Tibetan Plateau. These high-K calc-alkaline volcanic rocks were formed between 36 and 34 Ma, characterized by high Mg# values, high concentrations of TiO2 and P205, 87Sr/S6Sr ratios of 0. 704682--0. 706 112, and aNd（t） values of - 1.2 to 1.6. There is a lack of reasonable explanations for sour- cing and origin of magmas that formed the rocks with high Mg# values and TiO2 and P2O5 enrichments, which makes the previous research results still controversial. This study reviews the geochemical characteristics of Nadingcuo volcanic rocks and the data we have newly found in our fieldwork. We give some new interpretation to the magmatic evolution of the basaltic magmas in the discussed area dominated by fractional crystallization. The geochemistry of trachyandesite and trachyte units in the studied area is indicative of formation from mantle- derived magmas that mixed with crustal materials. The high values of Mg# and TiO2 and P205 enrichment in these units are evident to show the mixing between mantle-derived magmas with -30-40 wt.% rhyolitic melt or assimilation of a similar amount of felsic rocks. The geochemistry of basaltic rocks in the area also suggests that the Nadingcuo basalts may have been derived from an ocean island basalt （OIB） -type source that contained and was mixed with ancient mantle wedge derived material, indicating that a 36-34 Ma asthenospheric upwelling e- vent in the Qiangtang area may relate to the northward subduction of Indian lithospheric mantle and the south- ward subduction of Asian lithospherie mantle. This upwelling of asthenospherie material was centered in the southern Qiangtang area between 36 and 34 Ma, while the northward movement of the Indian Craton caused this upwelling mantle flow to continuously migrate northward, resulting in the current centering of this upwelling in the Hoh Xil-Kunlun region.展开更多
The Dahongliutan granitic pluton,in the eastern part of the West Kunlun orogenic belt,provides significant insights for studying the tectonic evolution of West Kunlun.This paper presents a systematic study of LA-ICP-M...The Dahongliutan granitic pluton,in the eastern part of the West Kunlun orogenic belt,provides significant insights for studying the tectonic evolution of West Kunlun.This paper presents a systematic study of LA-ICP-MS zircon U Pb age,major and trace elements,Sr-Nd-Hf isotopes,and the first detailed Li isotope analysis of the Dahongliutan pluton.LA-ICP-MS zircon U Pb dating shows that the Dahongliutan granites were emplaced in the Late Triassic((213±2.1)Ma).Geochemical data show relatively high SiO2 contents(68.45 wt%73.62 wt%)and aluminum saturation index(A/CNK=1.111.21)indicates peraluminous high-K calc-alkaline granite.The Dahongliutan granites are relatively high in light rare earth elements(LREE)and large ion lithophile elements(LILEs)(e.g.,Rb,K,Th),and relatively depleted in high field strength elements(HFSEs)(e.g.,Nb,Ta,P,Ti).TheεNd(t)values range from 8.71 to 4.73,and(87Sr/86Sr)i=0.70870.71574.Zircons from the pluton yield 176Hf/177Hf values of 0.2826181 to 0.2827683,andεHf(t)values are around 0;the two-stage Hf model ages range from 0.974 to 1.307 Ga.Theδ7Li values are 0.76‰3.25‰,with an average of 2.53‰.Isotopic compositions of the pluton suggest a mixed trend between the partial melting of the Middle Proterozoic ancient crustal material and a juvenile mantle-derived material.This study infers that the Dahongliutan rock mass is formed in the post-collisional extension environment,when the collision between South Kunlun and the Tianshuihai terranes results in the closure of the Palaeo-Tethys.The mantle-derived magma results in partial melting of the lower crust.展开更多
The main rock types of the Boluonuo and Daguangding plutons are diorite, quartz diorite, tonalite, granodiorite, and subordi- nate plagioclase-bearing hornblendite and hornblende gabbro. Zircon SHRIMP U-Pb dating for ...The main rock types of the Boluonuo and Daguangding plutons are diorite, quartz diorite, tonalite, granodiorite, and subordi- nate plagioclase-bearing hornblendite and hornblende gabbro. Zircon SHRIMP U-Pb dating for a quartz diorite of the Boluo- nuo pluton suggests that the pluton was emplaced at about 296 ± 4 Ma. Plagioclase-bearing hornblendites show typical cumu- lative textures, which, in combination with their convex-upward REE patterns and the large variation of compatible elements such as Co, V and Sc, suggests that these hornblendites formed through accumulation of hornblende during magma evolution. Microgranular mafic enclaves （MMEs） are common in the Boluonuo and Daguangding intermediate to felsic plutons. Many plagioclase grains show compositional and textural disequilibrium, with calcium-rich cores （An46-50） mantled abruptly by sodium-rich plagioclase （An26-33）. Whole-rock samples of the plutons are characterized by quite negative εNd（t） values （-16.5 to -11.8） and εNt（t） values （-22.5 to -16.8）, and the εNd（t） values are negatively correlated with silica contents. All these fea- tures suggest that the intermediate to felsic plutons formed through magma mixing of enriched mantle-derived, evolved basal- tic magma with granitic, crustal melts, followed by fractional crystallization of mainly hornblende and small amounts of py- roxene, apatite and zircon. The hornblende-dominated fractionation contributed significantly to the adakite-like features of the intermediate to felsic plutons, like the high Sr and Sr/Y ratios and low Yb abundance. In addition, the Boluonuo and Daguang- ding plutons are highly enriched in LILEs （e.g., Ba and Sr）, but depleted in HFSEs （e.g., Nb, Zr and Ti）, which is typical of arc magmas. Therefore, the formation of Boluonuo and Daguangding plutons was probably related to the subduction of the Paleo-Asian oceanic slab beneath the North China Craton in the Paleozoic.展开更多
基金supported by the National Major Fundamental Research and Development Project(No.G2000046703).
文摘The major elements, trace elements. K-Ar age and Sr-Nd-Pb isotopie systems ofthe Cenozoic volcanic rocks in Daheishan Island and Cishan, Penglai, Shandong Province aremeasured. The volcanic rocks ( olivine-nephelinite and nephcline-basanite ) in Daheishan Islanderupted periodically in an interval of 0.32 Ma, from 8.72 Ma. 8.39 Ma. 8.08 Ma to 7.73 Ma. Thevolcanic rocks arc all rich in light REEs. They are similar to the OIB-type alkali basalt in thetrace elements normalized model by primordial mantle: rich in high field elements such as Nb and Ta,and imcompatible elements such as Cs. Rb, Ba, Th. U. The volcanic rocks show a depletion of K andRb elements. It is suggested by the trace elements that the olivine-nephelinite in Daheishan Islandis originated from deep resources under the continental mantle. ε Nd (0) values of the volcanicrocks in Daheishan Island and Cishan are 5.31～8.51 and 7.33 respectively, suggesting that thevolcanic rocks are from the depleted mantle resources, which have higher Sm/Nd ratios than the CHUR.^(143)Nd /^(144)Nd ratios ot Daheishan Island olivine-nephelinite and Cishan alkali basalts are0.512 910～0.513 074 and 0.513 014 respectively. The ^(87)Sr /^(86)Sr of Daheishan Island volcanicrocks are lower than that of Cishan, 0.703 427 ～0.703 482 and 0.703 895 respectively. The DaheishanIsland olivine-nephelinite has the Pb isotopie values as follows: ^(206)Pb/^(204)Pb= 18.028 9～17.972 8. ^(207)Pb / ^(204)Pb = 15.435 8 ～15.402 2 and ^(208)Pb /^(204)Pb = 38.087 6～37.997 5.lower than those of Cishan basanite. The Cishan basanite has ^(206)Pb/^(204)Pb= 18.240 1. ^(207)Pb/^(204)Pb= 15.564 5 and ^(208)Pb /^(204)Pb = 38.535. The authors suggest that theolivine-nephelinite in Daheishan Island is similar to the E-type MORB or Hawaii OIB, and the alkalibasalts in Cishan similar to the Kerguelen OIB. The dominant mantle components of DM+PREMA andperhaps DM ( Dupal type ) are the dominant mantle components for volcanic rocks in Daheishan Islandand Cishan. The PREMA component plays an important role.
基金Supported by project of National Natural Science Foundation of China(41172056)
文摘The Nadingcuo volcanic rock suite is the most volmninous Cenozoic volcanic suite in the southern Qiangtang area of the northern Tibetan Plateau. These high-K calc-alkaline volcanic rocks were formed between 36 and 34 Ma, characterized by high Mg# values, high concentrations of TiO2 and P205, 87Sr/S6Sr ratios of 0. 704682--0. 706 112, and aNd（t） values of - 1.2 to 1.6. There is a lack of reasonable explanations for sour- cing and origin of magmas that formed the rocks with high Mg# values and TiO2 and P2O5 enrichments, which makes the previous research results still controversial. This study reviews the geochemical characteristics of Nadingcuo volcanic rocks and the data we have newly found in our fieldwork. We give some new interpretation to the magmatic evolution of the basaltic magmas in the discussed area dominated by fractional crystallization. The geochemistry of trachyandesite and trachyte units in the studied area is indicative of formation from mantle- derived magmas that mixed with crustal materials. The high values of Mg# and TiO2 and P205 enrichment in these units are evident to show the mixing between mantle-derived magmas with -30-40 wt.% rhyolitic melt or assimilation of a similar amount of felsic rocks. The geochemistry of basaltic rocks in the area also suggests that the Nadingcuo basalts may have been derived from an ocean island basalt （OIB） -type source that contained and was mixed with ancient mantle wedge derived material, indicating that a 36-34 Ma asthenospheric upwelling e- vent in the Qiangtang area may relate to the northward subduction of Indian lithospheric mantle and the south- ward subduction of Asian lithospherie mantle. This upwelling of asthenospherie material was centered in the southern Qiangtang area between 36 and 34 Ma, while the northward movement of the Indian Craton caused this upwelling mantle flow to continuously migrate northward, resulting in the current centering of this upwelling in the Hoh Xil-Kunlun region.
基金Project(2017YFC0602701)supported by the National Key Research and Development Plan,ChinaProject(DD20160004-8-3)supported by the Geological Survey of China
文摘The Dahongliutan granitic pluton,in the eastern part of the West Kunlun orogenic belt,provides significant insights for studying the tectonic evolution of West Kunlun.This paper presents a systematic study of LA-ICP-MS zircon U Pb age,major and trace elements,Sr-Nd-Hf isotopes,and the first detailed Li isotope analysis of the Dahongliutan pluton.LA-ICP-MS zircon U Pb dating shows that the Dahongliutan granites were emplaced in the Late Triassic((213±2.1)Ma).Geochemical data show relatively high SiO2 contents(68.45 wt%73.62 wt%)and aluminum saturation index(A/CNK=1.111.21)indicates peraluminous high-K calc-alkaline granite.The Dahongliutan granites are relatively high in light rare earth elements(LREE)and large ion lithophile elements(LILEs)(e.g.,Rb,K,Th),and relatively depleted in high field strength elements(HFSEs)(e.g.,Nb,Ta,P,Ti).TheεNd(t)values range from 8.71 to 4.73,and(87Sr/86Sr)i=0.70870.71574.Zircons from the pluton yield 176Hf/177Hf values of 0.2826181 to 0.2827683,andεHf(t)values are around 0;the two-stage Hf model ages range from 0.974 to 1.307 Ga.Theδ7Li values are 0.76‰3.25‰,with an average of 2.53‰.Isotopic compositions of the pluton suggest a mixed trend between the partial melting of the Middle Proterozoic ancient crustal material and a juvenile mantle-derived material.This study infers that the Dahongliutan rock mass is formed in the post-collisional extension environment,when the collision between South Kunlun and the Tianshuihai terranes results in the closure of the Palaeo-Tethys.The mantle-derived magma results in partial melting of the lower crust.
基金supported by National Natural Science Foundation of China (Grant Nos. 90914001,41121062)Fundamental Research Funds (Grant Nos. 2012CSJ04,2012CSJ04)
文摘The main rock types of the Boluonuo and Daguangding plutons are diorite, quartz diorite, tonalite, granodiorite, and subordi- nate plagioclase-bearing hornblendite and hornblende gabbro. Zircon SHRIMP U-Pb dating for a quartz diorite of the Boluo- nuo pluton suggests that the pluton was emplaced at about 296 ± 4 Ma. Plagioclase-bearing hornblendites show typical cumu- lative textures, which, in combination with their convex-upward REE patterns and the large variation of compatible elements such as Co, V and Sc, suggests that these hornblendites formed through accumulation of hornblende during magma evolution. Microgranular mafic enclaves （MMEs） are common in the Boluonuo and Daguangding intermediate to felsic plutons. Many plagioclase grains show compositional and textural disequilibrium, with calcium-rich cores （An46-50） mantled abruptly by sodium-rich plagioclase （An26-33）. Whole-rock samples of the plutons are characterized by quite negative εNd（t） values （-16.5 to -11.8） and εNt（t） values （-22.5 to -16.8）, and the εNd（t） values are negatively correlated with silica contents. All these fea- tures suggest that the intermediate to felsic plutons formed through magma mixing of enriched mantle-derived, evolved basal- tic magma with granitic, crustal melts, followed by fractional crystallization of mainly hornblende and small amounts of py- roxene, apatite and zircon. The hornblende-dominated fractionation contributed significantly to the adakite-like features of the intermediate to felsic plutons, like the high Sr and Sr/Y ratios and low Yb abundance. In addition, the Boluonuo and Daguang- ding plutons are highly enriched in LILEs （e.g., Ba and Sr）, but depleted in HFSEs （e.g., Nb, Zr and Ti）, which is typical of arc magmas. Therefore, the formation of Boluonuo and Daguangding plutons was probably related to the subduction of the Paleo-Asian oceanic slab beneath the North China Craton in the Paleozoic.
