本文選題：西北印度洋中脊 + 玄武巖��； 參考：《海洋科學(xué)》2016年08期

【摘要】：利用全球巖石地球化學(xué)數(shù)據(jù)庫(Pet DB)中有關(guān)卡爾斯伯格洋脊(CR)、北中印度洋脊(NCIR)及南中印度洋脊(SCIR)玄武巖的微量元素及同位素組成數(shù)據(jù),分析了玄武巖的元素地球化學(xué)特征及其沿脊軸的變化,旨在探討玄武巖源區(qū)地幔的(不)均一性及巖漿作用過程的差異。初步研究結(jié)果表明:CR、NCIR及SCIR玄武巖組成相近,僅在個別脊段表現(xiàn)有微量稀土元素和同位素組成上的差異,玄武巖整體與N-MORB組成特征相近,與先前通常認(rèn)為的典型印度洋中脊玄武巖不同。玄武質(zhì)巖漿主要源自尖晶石二輝橄欖巖地幔的熔融,巖漿源區(qū)主要由兩個地幔端元構(gòu)成,即以虧損型地幔(DMM)為主(69%),其次為富集型地幔(EMⅡ,27%)。富集組分可能源自古老陸殼物質(zhì)的混染。自CR經(jīng)NCIR到SCIR整個印度洋中脊西北分支玄武巖的Sr、Nd及Pb同位素組成表現(xiàn)出均一性,表明巖漿源區(qū)地幔組成相近。在SCIR 19°S附近脊段巖漿源區(qū)地幔存在有不均一性,有EMⅡ型地幔端元混入的跡象。在CR 3.5°N附近脊段,玄武巖明顯富集K、Ba、La及U等微量元素,但由于缺少同位素數(shù)據(jù),源區(qū)地幔特征有待進(jìn)一步研究。在上述研究成果的基礎(chǔ)上,提出了該區(qū)大比例尺的調(diào)查填圖及密集采樣和精細(xì)室內(nèi)分析是CR深入研究的基礎(chǔ),同時加強(qiáng)Sr、Nd、Pb及Re、Os、Be等同位素分析測試,可提供揭示CR地幔不均一性的可靠依據(jù),而厘清印度洋型地幔對CR的影響程度則有助于深入認(rèn)識地幔不均一性的成因及地幔動力學(xué)過程。
[Abstract]:Using the data of trace elements and isotopic compositions of basalts from the global petrogeochemical database (Pet DB) relating to the Karlsberg Ridge, the North Central Indian Ridge (NCIRs) and the South Indian Ridge (SCIRR),The elemental geochemical characteristics of basalts and their variations along the ridge axis are analyzed in order to explore the (inhomogeneity) of mantle and the differences of magmatic processes in basalt source regions.The preliminary results show that the composition of SCIR basalts is similar to that of SCIR basalts, and only shows the differences of trace rare earth elements and isotopic compositions in individual ridges. The basalts as a whole are similar to those of N-MORB rocks.It is different from the typical Indian Ocean ridge basalt.Black Tortoise magma is mainly derived from the melting of the spinel peridotite mantle. The magmatic source region is mainly composed of two mantle endants, namely, the depleted mantle (DMMM) and the enriched mantle (EM 鈪，

本文編號：1741022