本文選題：地幔結(jié)構(gòu)　切入點(diǎn)：地幔成分　出處：《中國科學(xué):地球科學(xué)》2017年10期 　論文類型：期刊論文

【摘要】：對(duì)地幔的地球化學(xué)研究為理解地球的形成和演化、其內(nèi)部結(jié)構(gòu)以及地幔動(dòng)力學(xué)提供了重要制約.全地球的成分是通過由地幔巖石與球粒隕石對(duì)比所得到,并由此引出了球粒隕石質(zhì)地球模型.這個(gè)模型認(rèn)為地球難熔元素比例與球粒隕石相同,但揮發(fā)份相對(duì)虧損.洋島玄武巖可能是源于地幔柱深部成因,進(jìn)而成為研究深部地球的獨(dú)特途徑.洋島玄武巖同位素組成變化可用有限幾個(gè)地幔端元(例如,DMM、EM1、EM2和HIMU)來描述,由此用來解譯重要的地幔過程.地殼物質(zhì)通過俯沖和拆沉進(jìn)入深部地幔,對(duì)地幔不均一的形成起到了重要作用.然而,這些地殼物質(zhì)如何由部分熔融所提取,例如洋島玄武巖成因中貧橄欖石巖石的作用,仍是熱點(diǎn)爭(zhēng)論話題.高~3He/~4He地幔的位置和成因仍有爭(zhēng)議,存在從下地幔未演化(或弱演化)的原始物質(zhì)到淺部成因的高程度演化物質(zhì)的看法,后者包括古老熔融殘留、弧下鎂鐵質(zhì)堆晶和再循環(huán)含水礦物.可能存在的核幔相互作用被假定為洋島玄武巖中諸如放射成因~(186)Os以及Fe和Ni的富集之類地球化學(xué)特征形成的原因.諸如~(142)Nd、~(182)W和Xe同位素之類的短壽命核素的微小但重要的變化在古老和現(xiàn)代巖石中均有報(bào)道,這暗示地幔必須在地球形成后100Myr內(nèi)即發(fā)生分異,而且地幔并未被對(duì)流所有效均一化.
[Abstract]:Geochemical studies of the mantle provide important constraints for understanding the formation and evolution of the Earth, its internal structure and mantle dynamics. The composition of the whole Earth is derived from the comparison of mantle rocks with chondrites. The chondrite-like earth model is derived. The model holds that the ratio of refractory elements to chondrites is the same as that of chondrites, but the volatiles are relatively depleted. The oceanic island basalts may have originated from the deep mantle plume. The variations in isotopic composition of oceanic basalts can be described by a limited number of mantle end elements (such as DMMMU EM1 EM2 and HIMU). This is used to interpret important mantle processes. Crustal matter enters the deep mantle through subduction and deconvolution, which plays an important role in the formation of mantle heterogeneity. However, how these crustal materials are extracted by partial melting, For example, the role of olivine rocks in the genesis of oceanic basalts is still a hot topic of debate. There is a perception of a high level of evolution from unevoluted (or weakly evolved) primitive matter in the lower mantle to a highly evolved material of shallow origin, which includes ancient molten residues, Subarc magnesia-ferrite heaps and recycled water-bearing minerals. The possible core-mantle interaction is assumed to be the cause of the formation of geochemical characteristics in oceanic island basalts, such as the enrichment of radiogenic basalts such as 186Os and Fe and Ni. Minor but important changes in short-lived nuclides such as Xe isotopes have been reported in both ancient and modern rocks. This implies that the mantle must be differentiated within 100 Myr after the formation of the Earth and that the mantle is not effectively homogenized by convection.
【作者單位】： Department
【基金】：美國國家科學(xué)基金會(huì)項(xiàng)目(編號(hào):NSF EAR-1524387) 國家自然科學(xué)基金項(xiàng)目(批準(zhǔn)號(hào):41590620)資助
【分類號(hào)】：P542.5;P588.145

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