Liquid immiscibility of boninite in Xiangcheng, southwestern China, and;its implication to genetic relationship between boninite and komatiitic;basalt

	Liquid immiscibility of boninite in Xiangcheng, southwestern China, and;its implication to genetic relationship between boninite and komatiitic;basalt
	Hou, ZQ 3; Qu, XM ; Urabe, T ; Takagi ; Naito
刊名	ACTA GEOLOGICA SINICA-ENGLISH EDITION
	2001
卷号	75 期号:1 页码:74-93
关键词	boninite komatiitic basalt liquid immiscibility Xiangcheng area of Sichuan
ISSN号	1000-9515
英文摘要	Boninitic rocks and associated high-magnesian basalt and high-iron tholeiite in the Xiangcheng area constitute the basal horizon of the are volcanic sequence in the Triassic Yidun Island-Are, southwestern China. The boninite occurs as pillow, massive and ocellar lavas; the last one possesses well-developed globular structure and alternates with the former two. The boninite is characterized by the absence of phenocrysts of olivine and low-Ca pyroxenes and by low CaO/Al2O3 ratios (<0.67) and high Cr (> 1000 ppm) and Ni (> 250 ppm). The normalized abundance patterns (NAP) of trace elements to primitive mantle are similar to the NAP of low-Ca modern boninites and SHMB in the Archaean and Proterozoic.;As a mechanism of ocellar texture, liquid immiscibility in boninite is supported by the following lines of evidence: (a) sharp contact between ocelli and matrix, (b) constant volumetric ratios of ocelli/matrix and common coalescence of ocelli in ocellar rocks, (c) identical micro-spinifex textures and mineral assemblages with different modal mineral contents in ocelli-matrix pairs, (d) bubbles and acicular clinopyroxene crystal strand over the boundary between ocelli and matrix, and (e) chemical compositions of ocelli and matrix corresponding to high-Mg andesite and komatiitic basalt, respectively. The close association and geochemical similarities between ocellar boninites and pillow boninite/massive boninite suggest that these are comagmatic rocks. The primary features of the ocellar boninite indicated by high Mg/(Mg+Fe2+) ratio and high Cr and Ni abundance show that liquid immiscibility took place in the early evolution stage of the boninitic magma. The miscibility gap in boninite which is smaller than that in tholeiite is likely to be due to the low FeO/MgO+FeO ratio and high MgO content of the boninitic magma.;The association of komatiite-komatiitic basalt-boninite (or SHMB and the immiscibility phenomenon in high-Mg lavas in some Archaean greenstone belts and ophiolites is also reexamined. It is considered that liquid immiscibility in parental boninitic magma probably produced komatiitic basalt, which often occurs in close association with boninite (or high-Mg andesite).
学科主题	火成岩岩石学
WOS关键词	HIGH-MAGNESIAN ANDESITES ; SETOUCHI VOLCANIC BELT ; OPHIOLITIC BASALTS ; ARCHEAN VARIOLITES ; MUNRO-TOWNSHIP ; PETROGENESIS ; ROCKS ; JAPAN ; GEOCHEMISTRY ; COEFFICIENTS
WOS研究方向	Geology
语种	英语
出版者	GEOLOGICAL SOC CHINA
WOS记录号	WOS:000168021700009
内容类型	期刊论文
源URL	[http://119.78.100.197/handle/2HKVOGP0/37469]
专题	中国地质科学院地质研究所
作者单位	1.Chinese Acad Geol Sci, Beijing 100037, Peoples R China. 2.Geol Survey Japan, Tsukuba, Ibaraki 305, Japan. 3.中国地质科学院地质研究所
推荐引用方式 GB/T 7714	Hou, ZQ,Qu, XM,Urabe, T,et al. Liquid immiscibility of boninite in Xiangcheng, southwestern China, and;its implication to genetic relationship between boninite and komatiitic;basalt[J]. ACTA GEOLOGICA SINICA-ENGLISH EDITION,2001,75(1):74-93.
APA	Hou, ZQ,Qu, XM,Urabe, T,Takagi,&Naito.(2001).Liquid immiscibility of boninite in Xiangcheng, southwestern China, and;its implication to genetic relationship between boninite and komatiitic;basalt.ACTA GEOLOGICA SINICA-ENGLISH EDITION,75(1),74-93.
MLA	Hou, ZQ,et al."Liquid immiscibility of boninite in Xiangcheng, southwestern China, and;its implication to genetic relationship between boninite and komatiitic;basalt".ACTA GEOLOGICA SINICA-ENGLISH EDITION 75.1(2001):74-93.