Flat rare earth element patterns as an indicator of cumulate processes in the Lesser Qinling carbonatites, China

	Flat rare earth element patterns as an indicator of cumulate processes in the Lesser Qinling carbonatites, China
	Cheng Xu; Ian H.Campbell; Charlotte M.Allen; Zhilong Huang; Liang Qi; Huan Zhang; Guishan; Zhang
	2007
发表期刊	Lithos
卷号	95 期号:3-4 页码:267-278
摘要	The Lesser Qinling carbonatite dykes are mainly composed of calcites. They are characterized by unusually high heavy rare earth element concentrations (HREE; e.g. Yb > 30 ppm) and flat to weakly light rare earth element (LREE) enriched chondrite-normalized patterns (La/Yb_n = 1.0–5.5), which is in marked contrast with all other published carbonatite data. The trace element contents of calcite crystals were measured in situ by laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS). Some crystals show reduced LREE from core to rim, whereas their HREE compositions are relatively constant. The total REE contents and chondrite-normalized REE patterns from the cores of carbonate crystals are similar to those of the whole rock. The carbon and oxygen isotopic compositions of calcites fall within the range of primary, mantle-derived carbonatites. The initial Sr isotopic compositions (0.70480–0.70557) of calcites are consistent with an EM1 source or mixing between HIMU and EM1 mantle sources. However these sources cannot produce carbonatite parental magmas with a flat or slightly LREE enrichment pattern by low degrees of partial melting. Analyses of carbonates from other carbonatites show that carbonates have nearly flat REE pattern if they crystallize from a LREE enriched carbonatite melt. This implies that when carbonates crystallize from a carbonatite melt the calcite/melt partition coefficients (D) for HREE are much greater than the D for the LREE. The nearly flat REE patterns of the Lesser Qinling carbonatites can be explained if they are carbonate cumulates that contain little trapped carbonatite melt. Strong enrichment of HREE in the carbonatites may require their derivation by small degrees of melting from a garnet-poor source.
关键词	Carbonatites Rare Earth Elements Crystal Cumulates Lesser Qinling
学科领域	矿床地球化学
收录类别	SCI
语种	英语
文献类型	期刊论文
条目标识符	http://ir.gyig.ac.cn/handle/352002/6795
专题	矿床地球化学国家重点实验室_矿床地球化学国家重点实验室_期刊论文
推荐引用方式 GB/T 7714	Cheng Xu,Ian H.Campbell,Charlotte M.Allen,et al. Flat rare earth element patterns as an indicator of cumulate processes in the Lesser Qinling carbonatites, China[J]. Lithos,2007,95(3-4):267-278.
APA	Cheng Xu.,Ian H.Campbell.,Charlotte M.Allen.,Zhilong Huang.,Liang Qi.,...&Zhang.(2007).Flat rare earth element patterns as an indicator of cumulate processes in the Lesser Qinling carbonatites, China.Lithos,95(3-4),267-278.
MLA	Cheng Xu,et al."Flat rare earth element patterns as an indicator of cumulate processes in the Lesser Qinling carbonatites, China".Lithos 95.3-4(2007):267-278.

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