Some basic concepts and problems on the petrogenesis of intra-plate   ocean island basalts

doi:10.1007/s11434-009-0668-3

CORC > 北京大学 > 地球与空间科学学院

	Some basic concepts and problems on the petrogenesis of intra-plate ocean island basalts
	Niu Yaoling
刊名	科学通报英文版
	2009
关键词	ocean islands intra-plate magmatism mantle source heterogeneity mantle metasomatism seismic low velocity zone processes EAST PACIFIC RISE LOW-VELOCITY ZONE BENEATH MIDOCEAN RIDGES TRACE-ELEMENT EVIDENCE CONTINENTAL-CRUST MANTLE PLUMES PRESSURE-DEPENDENCE ISOTOPIC EVIDENCE ALKALINE LAVAS DEEP MANTLE
DOI	10.1007/s11434-009-0668-3
英文摘要	Basaltic magmatism that builds intra-plate ocean islands is often considered to be genetically associated with "hotspots" or "mantle plumes". While there have been many discussions on why ocean island basalts (OIB) are geochemically highly enriched as an integral part of the mantle plume hypothesis, our current understanding on the origin of OIB source material remains unsatisfactory, and some prevailing ideas need revision. One of the most popular views states that OIB source material is recycled oceanic crust (ROC). Among many problems with the ROC model, the ocean crust is simply too depleted (e.g., [La/Sm](PM) <1) to be source material for highly enriched (e.g., [La/Sm](PM) >> 1) OIB. Another popular view states that the enriched component of OIB comes from recycled continental crust (RCC, i.e.; terrigenous sediments). While both CC and OIB are enriched in many incompatible elements (e.g., both have [La/Sm](PM) >> 1), the CC has characteristic enrichment in Pb and deletion in Nb, Ta, P and Ti. Such signature is too strong to be eliminated such that CC is unsuitable as source material for OIB. Plate tectonics and mantle circulation permit the presence of ROC and RCC materials in mantle source regions of basalts, but they must be volumetrically insignificant in contributing to basalt magmatism. The observation that OIB are not only enriched in incompatible elements, but also enriched in the progressively more incompatible elements indicates that the enriched component of OIB is of magmatic origin and most likely associated with low-degree melt metasomatism. H(2)O and CO(2) rich incipient melt may form in the seismic low velocity zone (LVZ). This melt will rise because of buoyancy and concentrate into a melt rich layer atop the LVZ to metasomatize the growing lithosphere, forming the metasomatic vein lithologies. Erupted OIB melts may have three components: (1) fertile OIB source material from depth that is dominant, (2) the melt layer, and (3) assimilation of the metasomatic vein lithologies formed earlier in the growing/grown lithosphere. It is probable that the fertile source material from depth may be (or contain) recycled ancient metasomatized deep portions of oceanic lithosphere. In any attempt to explain the origin of mantle isotopic end-members as revealed from global OIB data, we must (1) remember our original assumptions that the primitive mantle (PM) soon after the core separation was compositionally uniform/homogeneous with the core playing a limited or no role in causing mantle isotopic heterogeneity; (2) not use OIB isotopes to conclude about the nature and compositions of ultimate source materials without understanding geochemical consequences of subduction zone metamorphism; and (3) ensure that models and hypotheses are consistent with the basic petrology and major/trace element geochemistry.; Multidisciplinary Sciences; SCI(E); 8; REVIEW; 22; 4148-4160; 54
语种	英语
内容类型	期刊论文
源URL	[http://ir.pku.edu.cn/handle/20.500.11897/155879]
专题	地球与空间科学学院
推荐引用方式 GB/T 7714	Niu Yaoling. Some basic concepts and problems on the petrogenesis of intra-plate ocean island basalts[J]. 科学通报英文版,2009.
APA	Niu Yaoling.(2009).Some basic concepts and problems on the petrogenesis of intra-plate ocean island basalts.科学通报英文版.
MLA	Niu Yaoling."Some basic concepts and problems on the petrogenesis of intra-plate ocean island basalts".科学通报英文版 (2009).