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Composition of the Tarim mantle plume: Constraints from clinopyroxene antecrysts in the early Permian Xiaohaizi dykes, NW China
Wei, Xun1,2; Xu, Yi-Gang1; Luo, Zhen-Yu1; Zhao, Jian-Xin3; Feng, Yue-Xing3
2015-08-01
Source PublicationLITHOS
Volume230Issue:2015Pages:69-81
SubtypeArticle
AbstractNumerous alkaline basaltic dykes crosscut the Early Permian Xiaohaizi wehrlite in drill-cores and syenite intrusion in the Tarim large igneous province, NW China. One basaltic dyke contains abundant clinopyroxene macrocrysts with strong resorption textures. Such a textural disequilibrium is consistent with their contrasting chemistry between the macrocrysts (Mg# = 80-89) and the host dyke (Mg# = 39, corresponding to Mg# = 73 of clinopyroxene in equilibrium with the dyke), indicating that they are not phenocrysts. The clinopyroxene macrocrysts are characterized by low TiO2 (026-1.09 wt.%), Al2O3 (1.15-3.10 wt.%) and Na2O (0.16-0.37 wt.%), unlike those in mantle peridotites but resembling those in layered mafic intrusions in the same area. The clinopyroxene macrocrysts and the clinopyroxenes from the Xiaohaizi cumulate wehrlites define a coherent compositional trend and have identical trace element patterns, pointing to a comagmatic origin for these crystals. Accordingly, the macrocrysts cannot be xenoaysts foreign to the magmatic system. Rather they are antecrysts that crystallized from progenitor magmas and have been reincorporated into the host dyke before intrusion. The Sr-87/Sr-86(i) (0.7035-0.7037) and epsilon Nd-i (4.5-4.8) of the clinopyroxene macrocrysts with high Mg# (80-89) are apparently lower and higher than their respective ratios of the clinopyroxenes in the wehrlites (Mg# = 75-84, Sr-87/Sr-86(i) = 0.7038-0.7041, epsilon Nd-i = 1.0-1.9). This difference in isotopes can be accounted for by assimilation and fractional crystallization (AFC) process operated during the formation of the Xiaohaizi intrusion. In this sense, the clinopyroxene macrocrysts record the composition of the uncontaminated Tarim plume-derived melts. (C) 2015 Elsevier B.V. All rights reserved.
KeywordClinopyroxene Macrocryst Xiaohaizi Dyke Antecryst Tarim Large Igneous Province Assimilation And Fractional Crystallization
DOI10.1016/j.lithos.2015.05.010
Indexed BySCI
Language英语
WOS IDWOS:000357839000005
Citation statistics
Document Type期刊论文
Identifierhttp://ir.qdio.ac.cn/handle/337002/49206
Collection海洋地质与环境重点实验室
Affiliation1.Chinese Acad Sci, Guangzhou Inst Geochem, State Key Lab Isotope Geochem, Guangzhou 510640, Guangdong, Peoples R China
2.Chinese Acad Sci, Inst Oceanol, Key Lab Marine Geol & Environm, Qingdao 266071, Peoples R China
3.Univ Queensland, Sch Earth Sci, Radiogenic Isotope Facil, Brisbane, Qld 4072, Australia
First Author AffilicationInstitute of Oceanology, Chinese Academy of Sciences
Recommended Citation
GB/T 7714
Wei, Xun,Xu, Yi-Gang,Luo, Zhen-Yu,et al. Composition of the Tarim mantle plume: Constraints from clinopyroxene antecrysts in the early Permian Xiaohaizi dykes, NW China[J]. LITHOS,2015,230(2015):69-81.
APA Wei, Xun,Xu, Yi-Gang,Luo, Zhen-Yu,Zhao, Jian-Xin,&Feng, Yue-Xing.(2015).Composition of the Tarim mantle plume: Constraints from clinopyroxene antecrysts in the early Permian Xiaohaizi dykes, NW China.LITHOS,230(2015),69-81.
MLA Wei, Xun,et al."Composition of the Tarim mantle plume: Constraints from clinopyroxene antecrysts in the early Permian Xiaohaizi dykes, NW China".LITHOS 230.2015(2015):69-81.
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