Geochemistry of ultrapotassic volcanic rocks in Xiaogulihe NE China:   Implications for the role of ancient subducted sediments

doi:10.1016/j.lithos.2014.08.026

CORC > 北京大学 > 地球与空间科学学院

	Geochemistry of ultrapotassic volcanic rocks in Xiaogulihe NE China: Implications for the role of ancient subducted sediments
	Sun, Yang ; Ying, Jifeng ; Zhou, Xinhua ; Shao, Ji&apos ; Chu, Zhuyin ; Su, Benxun ; an
刊名	lithos
	2014
关键词	Ultrapotassic igneous rocks Sr-Nd-Hf-Pb-Os isotopes Sub-continental lithospheric mantle Ancient subducted sediments NE China LITHOSPHERIC MANTLE BENEATH CENOZOIC ALKALI BASALTS OCEAN ISLAND BASALTS RE-OS NORTHEAST CHINA TRACE-ELEMENT ISOTOPIC COMPOSITIONS EASTERN CHINA ASTHENOSPHERE INTERACTION CONTINENTAL-CRUST
DOI	10.1016/j.lithos.2014.08.026
英文摘要	The unique eruptions of ultrapotassic volcanic rocks in eastern China reported so far took place in the Xiaogulihe area of western Heilongjiang Province, NE China. These ultrapotassic rocks are characterized by extremely high 1(20 contents (>7 wt.%), abnormally unradiogenic Pb isotopic compositions ((206)pb/(204)pb = 16.44-16.55; (207)pb/(204)pb = 15.39-15.46; (208)pb/(204)pb = 36.35-36.61), and moderately high Sr-87/Sr-86 ratios (0.7053-0.7057), which can be basically correlated with those of ultrapotassic igneous rocks distributed widely in northwestern America and Aldan Shield. The positive correlation between Os-187/Os-188 and 1/Os argues that these ultrapotassic rocks have probably experienced negligible lower continental crust addition (less than 1%) during magma ascent. The high contents of K2O and negative correlation between Sr-87/Sr-86 and Pb-206/Pb-204 of these ultrapotassic rocks indicate the presence of a potassic phase, mostly phlogopite, in their mantle source. Their strong fractionation of rare earth elements and lack of Nd-Hf isotopic decoupling reveal a low-degree partial melting of garnet-bearing source rocks. In addition, the low CaO and Al2O3 contents of whole-rock compositions and low Fe/Mn ratios of olivine phenocryst chemistries suggest peridotites rather than pyroxenites as dominant source rocks for the Xiaogulihe ultrapotassic rocks. Based on these distinctive geochemical characteristics, we thus propose that the ultimate mantle source of the Xiaogulihe ultrapotassic volcanic rocks is phlogopite-bearing garnet peridotite within the lower part of the sub-continental lithospheric mantle (SCLM) that had been metasomatized by potassium-rich silicate melts. Combined with the unradiogenic Pb compositions, the most likely source of these potassium-rich silicate melts is the ancient subducted continental-derived sediments (>1.5 Ga). These ancient subducted sediments, possessing relatively low initial Pb isotopic compositions, had experienced large U/Pb fractionation during a subduction process, resulting in low-mu(U-238/Pb-204), and then accumulated in the mantle transition zone. The relatively low Sr-87/Sr-86 ratios of these ultrapotassic rocks also imply that their mantle source had evolved with low Rb/Sr ratios, which possibly resulted from the metasomatized melts derived from the ancient subducted sediments. This interpretation is quite different from previous hypotheses that attribute their unusual geochemical features to a dominantly asthenospheric source with a contribution from delaminated ancient SCLM, or a SCLM source that has been metasomatized by melts derived from deep asthenosphere or delaminated ancient lower continental crust. (C) 2014 Elsevier B.V. All rights reserved.; http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000345179900005&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701 ; Geochemistry & Geophysics; Mineralogy; SCI(E); 14; ARTICLE; jfying@mail.iggcas.ac.cn; 53-66; 208
语种	英语
内容类型	期刊论文
源URL	[http://ir.pku.edu.cn/handle/20.500.11897/207544]
专题	地球与空间科学学院
推荐引用方式 GB/T 7714	Sun, Yang,Ying, Jifeng,Zhou, Xinhua,et al. Geochemistry of ultrapotassic volcanic rocks in Xiaogulihe NE China: Implications for the role of ancient subducted sediments[J]. lithos,2014.
APA	Sun, Yang.,Ying, Jifeng.,Zhou, Xinhua.,Shao, Ji&apos.,Chu, Zhuyin.,...&an.(2014).Geochemistry of ultrapotassic volcanic rocks in Xiaogulihe NE China: Implications for the role of ancient subducted sediments.lithos.
MLA	Sun, Yang,et al."Geochemistry of ultrapotassic volcanic rocks in Xiaogulihe NE China: Implications for the role of ancient subducted sediments".lithos (2014).