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Yuexing Feng - One of the best experts on this subject based on the ideXlab platform.
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Petrology and Sr-Nd Isotopic Disequilibrium of the Xiaohaizi Intrusion, NW China: Genesis of Layered Intrusions in the Tarim Large Igneous Province
Journal of Petrology, 2014Co-Authors: Xun Wei, Chuanlin Zhang, Jianxin Zhao, Yuexing FengAbstract:Layered mafic intrusions (LMI) are sporadically distributed in the Early Permian Tarim large igneous province (LIP), NW China, and are crosscut by numerous contemporaneous dykes. The Xiaohaizi wehrlite intrusion is composed mainly of olivine (Fo69-75), clinopyroxene (Mg# = 75-84), intercumulus Plagioclase (An53-86) and Fe-Ti oxides. Both petrography and mineral compositions suggest that olivine and clinopyroxene crystallized earlier than Plagioclase and Fe-Ti oxides. The dykes are of alkali basalt to trachyandesite with low Mg# (35-39). The least-contaminated dykes display strong rare earth element (REE) fractionation, enrichment of Nb and Ta, and depletion of Pb relative to other similarly incompatible elements, bearing strong similarity to ocean island basalts (OIB). This, together with their positive epsilon Nd-i values (4.3-4.8), is consistent with derivation from an enriched asthenospheric mantle source. Clinopyroxenes in the wehrlites display convex-upward chondrite-normalized REE patterns. The melts in equilibrium with these clinopyroxenes have very similar trace element compositions to those of the crosscutting dykes, suggesting a similar mantle source shared by the Xiaohaizi wehrlite intrusion and dykes. The Xiaohaizi wehrlite intrusion is characterized by Sr-Nd isotopic disequilibrium between clinopyroxene and Plagioclase separates: Sr-87/(86)Sri (0.7038-0.7041) and epsilon Nd-i (1.0-1.9) of clinopyroxene are lower and higher than the respective ratios of intercumulus Plagioclase (Sr-87/Sr-86(i) = 0.7042-0.7043, epsilon Nd-i = 0.4-1.0). The Sr-87/(86)Sri and epsilon Nd-i of clinopyroxene separates correlate positively and negatively with Zr/ Nb, respectively, implying variable degrees of crustal contamination during the formation of the Xiaohaizi wehrlite intrusion. Sr-87/(86)Sri increases and epsilon Nd-i decreases with increasing Ca content of Plagioclase, indicating that higher An Plagioclases experienced higher degrees of contamination. This can be explained by assimilation of continental crust through a turbulent magma ascent (ATA) process. However, this ATA model fails to account for the positive correlation between the Mg# and epsilon Nd-i of clinopyroxene separates. The isotopic disequilibrium in the Xiaohaizi LMI is more probably generated during an assimilation and fractional crystallization process involving Archean-Neoproterozoic basement and carbonates as contaminants.
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petrology and sr nd isotopic disequilibrium of the xiaohaizi intrusion nw china genesis of layered intrusions in the tarim large igneous province
Journal of Petrology, 2014Co-Authors: Yigang Xu, Chuanlin Zhang, Jianxin Zhao, Yuexing FengAbstract:Layered mafic intrusions (LMI) are sporadically distributed in the Early Permian Tarim large igneous province (LIP), NW China, and are crosscut by numerous contemporaneous dykes. The Xiaohaizi wehrlite intrusion is composed mainly of olivine (Fo69-75), clinopyroxene (Mg# = 75-84), intercumulus Plagioclase (An53-86) and Fe-Ti oxides. Both petrography and mineral compositions suggest that olivine and clinopyroxene crystallized earlier than Plagioclase and Fe-Ti oxides. The dykes are of alkali basalt to trachyandesite with low Mg# (35-39). The least-contaminated dykes display strong rare earth element (REE) fractionation, enrichment of Nb and Ta, and depletion of Pb relative to other similarly incompatible elements, bearing strong similarity to ocean island basalts (OIB). This, together with their positive epsilon Nd-i values (4.3-4.8), is consistent with derivation from an enriched asthenospheric mantle source. Clinopyroxenes in the wehrlites display convex-upward chondrite-normalized REE patterns. The melts in equilibrium with these clinopyroxenes have very similar trace element compositions to those of the crosscutting dykes, suggesting a similar mantle source shared by the Xiaohaizi wehrlite intrusion and dykes. The Xiaohaizi wehrlite intrusion is characterized by Sr-Nd isotopic disequilibrium between clinopyroxene and Plagioclase separates: Sr-87/(86)Sri (0.7038-0.7041) and epsilon Nd-i (1.0-1.9) of clinopyroxene are lower and higher than the respective ratios of intercumulus Plagioclase (Sr-87/Sr-86(i) = 0.7042-0.7043, epsilon Nd-i = 0.4-1.0). The Sr-87/(86)Sri and epsilon Nd-i of clinopyroxene separates correlate positively and negatively with Zr/ Nb, respectively, implying variable degrees of crustal contamination during the formation of the Xiaohaizi wehrlite intrusion. Sr-87/(86)Sri increases and epsilon Nd-i decreases with increasing Ca content of Plagioclase, indicating that higher An Plagioclases experienced higher degrees of contamination. This can be explained by assimilation of continental crust through a turbulent magma ascent (ATA) process. However, this ATA model fails to account for the positive correlation between the Mg# and epsilon Nd-i of clinopyroxene separates. The isotopic disequilibrium in the Xiaohaizi LMI is more probably generated during an assimilation and fractional crystallization process involving Archean-Neoproterozoic basement and carbonates as contaminants.
Eric H Oelkers - One of the best experts on this subject based on the ideXlab platform.
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experimental determination of Plagioclase dissolution rates as a function of its composition and ph at 22 c
Geochimica et Cosmochimica Acta, 2014Co-Authors: Snorri Gudbrandsson, Domenik Wolffboenisch, Sigurdur R Gislason, Eric H OelkersAbstract:Abstract The steady-state, far-from-equilibrium dissolution rates of nine distinct Plagioclases ranging in composition from An2 to An89 were measured in mixed flow reactors at 22 ± 2 °C and pH from 2 to 11. The dissolution rates of all Plagioclases based on silica release show a common U-shaped behaviour as a function of pH, where rates decrease with increasing pH at acid condition but rise with increasing pH at alkaline conditions. Consistent with literature findings, constant pH Plagioclase dissolution rates increase with increasing anorthite content at acidic conditions; measured anorthite dissolution rates are ∼2.5 orders of magnitude faster than those of albite at pH ∼2. Perhaps more significantly, rates are independent of Plagioclase composition at alkaline conditions. Interpretation and data fitting suggests that Plagioclase dissolution rates are consistent with their control by the detachment of Si-rich activated complexes formed by the removal of Al from the mineral framework. Taking account of this mechanism and transition state theory yields equations describing Plagioclase dissolution rates (r+) as a function of both the mineral and aqueous fluid compositions found in natural Earth surface systems. For pH ⩾ 6 rates are consistent with Log ( r + / ( mol / cm 2 / s ) ) = 0.35 Log ( a H + 3 / a Al 3 + ) - 11.53 and for pH Log ( r + / ( mol / cm 2 / s ) ) = n acid Log ( a H + 3 / a Al 3 + ) + 0.033 An % - 14.77 where An% represents the percent anorthite in the Plagioclase solid solution, ai corresponds to the activity of the ith aqueous species, and nacid is given by n acid = 0.004 An % + 0.05 .
Chuanlin Zhang - One of the best experts on this subject based on the ideXlab platform.
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Petrology and Sr-Nd Isotopic Disequilibrium of the Xiaohaizi Intrusion, NW China: Genesis of Layered Intrusions in the Tarim Large Igneous Province
Journal of Petrology, 2014Co-Authors: Xun Wei, Chuanlin Zhang, Jianxin Zhao, Yuexing FengAbstract:Layered mafic intrusions (LMI) are sporadically distributed in the Early Permian Tarim large igneous province (LIP), NW China, and are crosscut by numerous contemporaneous dykes. The Xiaohaizi wehrlite intrusion is composed mainly of olivine (Fo69-75), clinopyroxene (Mg# = 75-84), intercumulus Plagioclase (An53-86) and Fe-Ti oxides. Both petrography and mineral compositions suggest that olivine and clinopyroxene crystallized earlier than Plagioclase and Fe-Ti oxides. The dykes are of alkali basalt to trachyandesite with low Mg# (35-39). The least-contaminated dykes display strong rare earth element (REE) fractionation, enrichment of Nb and Ta, and depletion of Pb relative to other similarly incompatible elements, bearing strong similarity to ocean island basalts (OIB). This, together with their positive epsilon Nd-i values (4.3-4.8), is consistent with derivation from an enriched asthenospheric mantle source. Clinopyroxenes in the wehrlites display convex-upward chondrite-normalized REE patterns. The melts in equilibrium with these clinopyroxenes have very similar trace element compositions to those of the crosscutting dykes, suggesting a similar mantle source shared by the Xiaohaizi wehrlite intrusion and dykes. The Xiaohaizi wehrlite intrusion is characterized by Sr-Nd isotopic disequilibrium between clinopyroxene and Plagioclase separates: Sr-87/(86)Sri (0.7038-0.7041) and epsilon Nd-i (1.0-1.9) of clinopyroxene are lower and higher than the respective ratios of intercumulus Plagioclase (Sr-87/Sr-86(i) = 0.7042-0.7043, epsilon Nd-i = 0.4-1.0). The Sr-87/(86)Sri and epsilon Nd-i of clinopyroxene separates correlate positively and negatively with Zr/ Nb, respectively, implying variable degrees of crustal contamination during the formation of the Xiaohaizi wehrlite intrusion. Sr-87/(86)Sri increases and epsilon Nd-i decreases with increasing Ca content of Plagioclase, indicating that higher An Plagioclases experienced higher degrees of contamination. This can be explained by assimilation of continental crust through a turbulent magma ascent (ATA) process. However, this ATA model fails to account for the positive correlation between the Mg# and epsilon Nd-i of clinopyroxene separates. The isotopic disequilibrium in the Xiaohaizi LMI is more probably generated during an assimilation and fractional crystallization process involving Archean-Neoproterozoic basement and carbonates as contaminants.
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petrology and sr nd isotopic disequilibrium of the xiaohaizi intrusion nw china genesis of layered intrusions in the tarim large igneous province
Journal of Petrology, 2014Co-Authors: Yigang Xu, Chuanlin Zhang, Jianxin Zhao, Yuexing FengAbstract:Layered mafic intrusions (LMI) are sporadically distributed in the Early Permian Tarim large igneous province (LIP), NW China, and are crosscut by numerous contemporaneous dykes. The Xiaohaizi wehrlite intrusion is composed mainly of olivine (Fo69-75), clinopyroxene (Mg# = 75-84), intercumulus Plagioclase (An53-86) and Fe-Ti oxides. Both petrography and mineral compositions suggest that olivine and clinopyroxene crystallized earlier than Plagioclase and Fe-Ti oxides. The dykes are of alkali basalt to trachyandesite with low Mg# (35-39). The least-contaminated dykes display strong rare earth element (REE) fractionation, enrichment of Nb and Ta, and depletion of Pb relative to other similarly incompatible elements, bearing strong similarity to ocean island basalts (OIB). This, together with their positive epsilon Nd-i values (4.3-4.8), is consistent with derivation from an enriched asthenospheric mantle source. Clinopyroxenes in the wehrlites display convex-upward chondrite-normalized REE patterns. The melts in equilibrium with these clinopyroxenes have very similar trace element compositions to those of the crosscutting dykes, suggesting a similar mantle source shared by the Xiaohaizi wehrlite intrusion and dykes. The Xiaohaizi wehrlite intrusion is characterized by Sr-Nd isotopic disequilibrium between clinopyroxene and Plagioclase separates: Sr-87/(86)Sri (0.7038-0.7041) and epsilon Nd-i (1.0-1.9) of clinopyroxene are lower and higher than the respective ratios of intercumulus Plagioclase (Sr-87/Sr-86(i) = 0.7042-0.7043, epsilon Nd-i = 0.4-1.0). The Sr-87/(86)Sri and epsilon Nd-i of clinopyroxene separates correlate positively and negatively with Zr/ Nb, respectively, implying variable degrees of crustal contamination during the formation of the Xiaohaizi wehrlite intrusion. Sr-87/(86)Sri increases and epsilon Nd-i decreases with increasing Ca content of Plagioclase, indicating that higher An Plagioclases experienced higher degrees of contamination. This can be explained by assimilation of continental crust through a turbulent magma ascent (ATA) process. However, this ATA model fails to account for the positive correlation between the Mg# and epsilon Nd-i of clinopyroxene separates. The isotopic disequilibrium in the Xiaohaizi LMI is more probably generated during an assimilation and fractional crystallization process involving Archean-Neoproterozoic basement and carbonates as contaminants.
Jianxin Zhao - One of the best experts on this subject based on the ideXlab platform.
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Petrology and Sr-Nd Isotopic Disequilibrium of the Xiaohaizi Intrusion, NW China: Genesis of Layered Intrusions in the Tarim Large Igneous Province
Journal of Petrology, 2014Co-Authors: Xun Wei, Chuanlin Zhang, Jianxin Zhao, Yuexing FengAbstract:Layered mafic intrusions (LMI) are sporadically distributed in the Early Permian Tarim large igneous province (LIP), NW China, and are crosscut by numerous contemporaneous dykes. The Xiaohaizi wehrlite intrusion is composed mainly of olivine (Fo69-75), clinopyroxene (Mg# = 75-84), intercumulus Plagioclase (An53-86) and Fe-Ti oxides. Both petrography and mineral compositions suggest that olivine and clinopyroxene crystallized earlier than Plagioclase and Fe-Ti oxides. The dykes are of alkali basalt to trachyandesite with low Mg# (35-39). The least-contaminated dykes display strong rare earth element (REE) fractionation, enrichment of Nb and Ta, and depletion of Pb relative to other similarly incompatible elements, bearing strong similarity to ocean island basalts (OIB). This, together with their positive epsilon Nd-i values (4.3-4.8), is consistent with derivation from an enriched asthenospheric mantle source. Clinopyroxenes in the wehrlites display convex-upward chondrite-normalized REE patterns. The melts in equilibrium with these clinopyroxenes have very similar trace element compositions to those of the crosscutting dykes, suggesting a similar mantle source shared by the Xiaohaizi wehrlite intrusion and dykes. The Xiaohaizi wehrlite intrusion is characterized by Sr-Nd isotopic disequilibrium between clinopyroxene and Plagioclase separates: Sr-87/(86)Sri (0.7038-0.7041) and epsilon Nd-i (1.0-1.9) of clinopyroxene are lower and higher than the respective ratios of intercumulus Plagioclase (Sr-87/Sr-86(i) = 0.7042-0.7043, epsilon Nd-i = 0.4-1.0). The Sr-87/(86)Sri and epsilon Nd-i of clinopyroxene separates correlate positively and negatively with Zr/ Nb, respectively, implying variable degrees of crustal contamination during the formation of the Xiaohaizi wehrlite intrusion. Sr-87/(86)Sri increases and epsilon Nd-i decreases with increasing Ca content of Plagioclase, indicating that higher An Plagioclases experienced higher degrees of contamination. This can be explained by assimilation of continental crust through a turbulent magma ascent (ATA) process. However, this ATA model fails to account for the positive correlation between the Mg# and epsilon Nd-i of clinopyroxene separates. The isotopic disequilibrium in the Xiaohaizi LMI is more probably generated during an assimilation and fractional crystallization process involving Archean-Neoproterozoic basement and carbonates as contaminants.
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petrology and sr nd isotopic disequilibrium of the xiaohaizi intrusion nw china genesis of layered intrusions in the tarim large igneous province
Journal of Petrology, 2014Co-Authors: Yigang Xu, Chuanlin Zhang, Jianxin Zhao, Yuexing FengAbstract:Layered mafic intrusions (LMI) are sporadically distributed in the Early Permian Tarim large igneous province (LIP), NW China, and are crosscut by numerous contemporaneous dykes. The Xiaohaizi wehrlite intrusion is composed mainly of olivine (Fo69-75), clinopyroxene (Mg# = 75-84), intercumulus Plagioclase (An53-86) and Fe-Ti oxides. Both petrography and mineral compositions suggest that olivine and clinopyroxene crystallized earlier than Plagioclase and Fe-Ti oxides. The dykes are of alkali basalt to trachyandesite with low Mg# (35-39). The least-contaminated dykes display strong rare earth element (REE) fractionation, enrichment of Nb and Ta, and depletion of Pb relative to other similarly incompatible elements, bearing strong similarity to ocean island basalts (OIB). This, together with their positive epsilon Nd-i values (4.3-4.8), is consistent with derivation from an enriched asthenospheric mantle source. Clinopyroxenes in the wehrlites display convex-upward chondrite-normalized REE patterns. The melts in equilibrium with these clinopyroxenes have very similar trace element compositions to those of the crosscutting dykes, suggesting a similar mantle source shared by the Xiaohaizi wehrlite intrusion and dykes. The Xiaohaizi wehrlite intrusion is characterized by Sr-Nd isotopic disequilibrium between clinopyroxene and Plagioclase separates: Sr-87/(86)Sri (0.7038-0.7041) and epsilon Nd-i (1.0-1.9) of clinopyroxene are lower and higher than the respective ratios of intercumulus Plagioclase (Sr-87/Sr-86(i) = 0.7042-0.7043, epsilon Nd-i = 0.4-1.0). The Sr-87/(86)Sri and epsilon Nd-i of clinopyroxene separates correlate positively and negatively with Zr/ Nb, respectively, implying variable degrees of crustal contamination during the formation of the Xiaohaizi wehrlite intrusion. Sr-87/(86)Sri increases and epsilon Nd-i decreases with increasing Ca content of Plagioclase, indicating that higher An Plagioclases experienced higher degrees of contamination. This can be explained by assimilation of continental crust through a turbulent magma ascent (ATA) process. However, this ATA model fails to account for the positive correlation between the Mg# and epsilon Nd-i of clinopyroxene separates. The isotopic disequilibrium in the Xiaohaizi LMI is more probably generated during an assimilation and fractional crystallization process involving Archean-Neoproterozoic basement and carbonates as contaminants.
Xun Wei - One of the best experts on this subject based on the ideXlab platform.
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Petrology and Sr-Nd Isotopic Disequilibrium of the Xiaohaizi Intrusion, NW China: Genesis of Layered Intrusions in the Tarim Large Igneous Province
Journal of Petrology, 2014Co-Authors: Xun Wei, Chuanlin Zhang, Jianxin Zhao, Yuexing FengAbstract:Layered mafic intrusions (LMI) are sporadically distributed in the Early Permian Tarim large igneous province (LIP), NW China, and are crosscut by numerous contemporaneous dykes. The Xiaohaizi wehrlite intrusion is composed mainly of olivine (Fo69-75), clinopyroxene (Mg# = 75-84), intercumulus Plagioclase (An53-86) and Fe-Ti oxides. Both petrography and mineral compositions suggest that olivine and clinopyroxene crystallized earlier than Plagioclase and Fe-Ti oxides. The dykes are of alkali basalt to trachyandesite with low Mg# (35-39). The least-contaminated dykes display strong rare earth element (REE) fractionation, enrichment of Nb and Ta, and depletion of Pb relative to other similarly incompatible elements, bearing strong similarity to ocean island basalts (OIB). This, together with their positive epsilon Nd-i values (4.3-4.8), is consistent with derivation from an enriched asthenospheric mantle source. Clinopyroxenes in the wehrlites display convex-upward chondrite-normalized REE patterns. The melts in equilibrium with these clinopyroxenes have very similar trace element compositions to those of the crosscutting dykes, suggesting a similar mantle source shared by the Xiaohaizi wehrlite intrusion and dykes. The Xiaohaizi wehrlite intrusion is characterized by Sr-Nd isotopic disequilibrium between clinopyroxene and Plagioclase separates: Sr-87/(86)Sri (0.7038-0.7041) and epsilon Nd-i (1.0-1.9) of clinopyroxene are lower and higher than the respective ratios of intercumulus Plagioclase (Sr-87/Sr-86(i) = 0.7042-0.7043, epsilon Nd-i = 0.4-1.0). The Sr-87/(86)Sri and epsilon Nd-i of clinopyroxene separates correlate positively and negatively with Zr/ Nb, respectively, implying variable degrees of crustal contamination during the formation of the Xiaohaizi wehrlite intrusion. Sr-87/(86)Sri increases and epsilon Nd-i decreases with increasing Ca content of Plagioclase, indicating that higher An Plagioclases experienced higher degrees of contamination. This can be explained by assimilation of continental crust through a turbulent magma ascent (ATA) process. However, this ATA model fails to account for the positive correlation between the Mg# and epsilon Nd-i of clinopyroxene separates. The isotopic disequilibrium in the Xiaohaizi LMI is more probably generated during an assimilation and fractional crystallization process involving Archean-Neoproterozoic basement and carbonates as contaminants.
