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

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	Flat rare earth element patterns as an indicator of cumulate processes in the Lesser Qinling carbonatites, China
	Guishan; Cheng Xu; Ian H.Campbell; Charlotte M.Allen; Zhilong Huang; Liang Qi; Huan Zhang; Zhang
刊名	Lithos
	2007
卷号	95 期号:3-4 页码:267-278
关键词	Carbonatites Rare Earth Elements Crystal Cumulates Lesser Qinling
英文摘要	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.
学科主题	矿床地球化学
语种	英语
公开日期	2017-12-19
内容类型	期刊论文
源URL	[http://ir.gyig.ac.cn:8080/handle/352002/6795]
专题	地球化学研究所_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	Guishan,Cheng Xu,Ian H.Campbell,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	Guishan.,Cheng Xu.,Ian H.Campbell.,Charlotte M.Allen.,Zhilong Huang.,...&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	Guishan,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.