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Geochemistry of the high-Mg andesites at Zhangwu, western Liaoning: Implication for delamination of newly formed lower crust

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Science china Earth Sciences 2007年第12期50卷 1773-1786页

作者： huang hua1,gao shan1,2.hu zhaochu1,liu xiaoming2.& yuan hongling2.1 state key laboratory of geological processes and mineral resources,china university of geosciences,wuhan 430074,china 2 state key laboratory of Continental Dynamics,Department of Geology,Northwest university,Xi’an 710069,china 1. state key laboratory of geological processes and mineral resources China University of Geosciences Wuhan 430074 China 2. state key laboratory of Continental Dynamics Department of Geology Northwest University Xi’an 710069 China

Ten volcanic samples at Zhangwu,western Liaoning Province,North china were selected for a sys-tematic geochemical,mineralogical and geochronological study,which provides an opportunity to ex-plore the interaction between the continental crust and mantle beneath the north margin of the North china *** one basalt sample(SiO2= 50.23%),the other nine samples are andesitic with SiO2 contents ranging from 53% to 59%.They have relatively high MgO(3.4%―6.1%,Mg#=50―64) and Ni and Cr contents(Ni 27×10?6―197×10?6,Cr 51×10?6―478×10?6).Other geochemical characteristics of Zhangwu high-Mg andesites(HMAs) include strong fractionation of light rare earth elements(LREE) from heavy rare earth elements(HREE),and Sr from Y,with La/Yb greater than 15,and high Sr/Y(34― 115).Zircons of andesite YX270 yield three age groups with no Precambrian age,which precludes ori-gin of the Zhangwu HMAs from the partial melting of the Precambrian *** oldest age group peaking at 253 Ma is interpreted to represent the collision of the Siberia block and the North china block,resulting in formation of the Central Asian orogenic belt by closure of the Mongol-Okhotsk *** intermediate age group corresponds to the basalt underplating which caused the wide-spread coeval granitoids in the North china craton with a peak 206Pb/238U age of 172 *** youngest age group gives a 206Pb/238U age of 126±2 Ma,which is interpreted as the eruption age of the Zhangwu *** high 87Sr/86Sri(126 Ma)>0.706 and low εNd(t)= ?6.36―?13.99 of the Zhangwu HMAs are distinct from slab *** common presence of reversely zoned clinopyroxene phenocrysts in the Zhangwu HMAs argues against the origin of the Zhangwu HMAs either from melting of the water saturated mantle or melting of the lower *** light of the evidence mentioned above,the envisaged scenario for the formation of the Zhangwu HMAs is related to the basaltic underplating at the base of the crust,which led to the thickening of the lower crust and

关键词： Zhangwu HMAs, basalt underplating, newly formed lower crust, delamination, North china craton

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Geochemistry of high-Mg andesites from the early Cretaceous Yixian Formation, western Liaoning: Implications for lower crustal delamination and Sr/Y variations

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Science china Earth Sciences 2006年第9期49卷 904-914页

作者： WANG Xiaorui1, gao shan1,2, liu {2.1, yuan Honglin1, hu zhaochu1, ZHANG Hong1,3 & WANG Xuance4 1. state key laboratory of Continental Dynamics, Department of Geology, Northwest university, Xi`an 710069, china 2. state key laboratory of geological processes and mineral resources, china university of geosciences, wuhan 430074, china 3. Shenyang Institute of Geology and mineral resources, Shenyang 110032, china 4. Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, china 1. state key laboratory of Continental Dynamics Department of Geology Northwest University Xi’an 710069 China 2. state key laboratory of geological processes and mineral resources China University of Geosciences Wuhan 430074 China 3. Shenyang Institute of Geology and mineral resources Shenyang 110032 China 4. Guangzhou Institute of Geochemistry Chinese Academy of Sciences Guangzhou 510640 China

85 volcanic rocks of the Yixian Formation from the Sihetun type section werecollected and analyzed for geochemical and isotopic compositions. Major element compositionsindicate that the Sihetun volcanic rocks are high magnesium andesites with some basalts occurring atthe bottom of section. The Sihetun high magnesium andesites (SiO_2 = 52.82-59.31 wt%, Al_2O_3=14.15-16.35wt%) show many characteristics of adakites such as depletion in heavy rare-earth elements(HREE; Yb = 1.03-1.88 μg/g) and Y(12-20 μg/g) and high Sr (620-1323 μg/g) and Sr/Y(32-88), withhigh La_N/Yb_N ratio (10-25). They share similar major and trace element characteristics to volcanicrocks from the Xinglonggou Formation except their lower Nd isotope ratios (^(143)Nd/^(144)Nd(130Ma) = 0.5118-0.5119, ε_(Nd) (130Ma) = -11.6-13.8, ^(87)Sr/^(86)Sr (130 Ma) = *** were interpreted in a way that eclogite that formed at the base of thickened Archean lowercrust of the North china craton foundered into the convecting mantle and subsequently melted andinteracted with peridotite. However, compared to the Xinglonggou volcanic rocks, the source of theSihetun magma contained more ancient continental crustal material in order to explain its evolved Ndisotopes. The age of the Sihetun Formation was 120 to 130 Ma, and this indicates that delaminationlasted to the early Cretaceous period. The Sr contents and Sr/Y ratios of the Sihetun high-Mgandesites show significant negative correlations with SiO_2 for samples with SiO_2 > 56%. Thesesuggest that the Sr and Sr/Y values were reduced due to fractional crystallization of ***, the effect of crystallization on volcanic Sr and Sr/Y ratio has to be taken intoaccount.

关键词： High-Mg andesite, Adakite, Yixian Formation, North china Craton, delamination.

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High-pressure synchrotron x-ray diffraction and Raman spectroscopic study of plumbogummite

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Chinese Physics B 2018年第1期27卷 541-546页

作者：康端巫翔袁冠黄圣轩牛菁菁高静秦善 key laboratory of Orogenic Belts and Crustal Evolution Ministry of Education School of Earth and Space SciencesPeking University state key laboratory of geological processes and mineral resources China University of Geosciences

PbA13（PO4）2（OH,H20）6, an important environmental mineral, is in-situ studied by synchrotron x-ray diffraction （XRD） and Raman scattering combined with diamond anvil cells （DACs） at pressures up to - 11.0 GPa and room temper- ature. The XRD results indicate that plumbogummite does not undergo a phase transition between 0 GPa and 10.9 GPa. Moreover, the c axis is more compressible than the a axis, revealing its anisotropic behavior. The pressure-volume data are fitted to the third-order Birch-Murnaghan equation of state to yield the plumbogummite bulk modulus K0 of 68（ I ） GPa and KU of 6.1. The [PO4]3 and [HPO4]2 Raman vibrational modes exhibit scale nearly linearly as a function of pressure. The [PO4]3 stretching modes are generally more sensitive to pressure than the bending modes. The Grfineisen parameters range from -0.07 to 1.19, with an arithmetic mean of approximately 0.39.

关键词： plumbogummite equation of state Grfineisen parameter diamond anvil cell

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