Mantle-derived magmas:intraplate,hot-spots and mid-ocean ridges

作     者：David H.Green Trevor J.Falloon 

作者机构：Earth Sciences School of Physical Sciences University of Tasmania 

出 版 物：《Science Bulletin》 (科学通报（英文版）)

年 卷 期：2015年第60卷第22期

页      面：1873-1900页

核心收录：

学科分类：070904[理学-构造地质学] 0709[理学-地质学] 07[理学] 

基　　金：the support of the Department of Geology/School of Earth Sciences at University of Tasmania the Research School of Earth Sciences, Australian National University At University of Tasmania, ‘Earth Sciences’ and ‘Centre for Ore Deposits and Exploration Studies (CODES)’ 

主　　题：幔源岩浆 大洋中脊 板内 地球化学分区 拉斑玄武岩 橄榄岩包体 橄榄玄武岩 地幔热柱 

摘      要：Primary or parental magmas act as probes to infer eruption and source temperatures for both mid-ocean ridge(MOR) and ‘hot-spot magmas(tholeiitic picrites).The experimental petrogenetic constraints(‘inverse experiments) argue for no significant temperature differences between them. However, there are differences in major, minor and trace elements which characterise geochemical, not thermal, anomalies beneath ‘hot-spots . We suggest that diapiric upwelling from interfaces(redox contrasts) between old subducted slab and normal MOR basalt source mantle is the major reason for the observed characteristics of island chain or ‘hot-spot *** basalts also include widely distributed volcanic centres containing lherzolite xenoliths, i.e. mantle-derived magmas. Inverse experiments on olivine basalt, alkali olivine basalt, olivine basanite, olivine nephelinite, olivine melilitite and olivine leucitite(lamproite) determined liquidus phases as a function of pressure, initially under anhydrous and CO2-absent conditions. Under C- and H-absent conditions, only tholeiites to alkali olivine basalts had Ol ? Opx ± Cpx as high-pressure liquidus *** of H2 O accessed olivine basanites at 2.5–3 GPa,*1,200 °C, but both CO2 and H2O were necessary to obtain saturation with Ol, Opx, Cpx and Ga at 2.5–3.5 GPa for olivine nephelinite and olivine melilitite. The forward and inverse experimental studies are combined to formulate a petrogenetic grid for intraplate, ‘hot-spot and MOR magmatism within the plate tectonics paradigm. The asthenosphere is geochemically zoned by slow upward migration of incipient melt. The solidus and phasestabilities of lherzolite with very small water contents(\3,000 ppm) determine the thin plate behaviour of the oceanic lithosphere and thus the Earth s convection in the form of plate tectonics. There is no evidence from the parental magmas of MOR and ‘hot-spots to support the‘deep mantle thermal plume hypothesis. The preferred alternativ