The evolution of refertilized lithospheric mantle beneath the northeastern Siberian craton:Links between mantle metasomatism,thermal state and diamond potential  

作　　者：Sergei Skuzovatov Vladislav S.Shatsky Alexey L.Ragozin Alexander P.Smelov 

机构地区：[1]Vinogradov Institute of Geochemistry,Russian Academy of Sciences,Siberian Branch,1A,Favorskogo Str.,Irkutsk 664033,Russia [2]Sobolev Institute of Geology and Mineralogy,Russian Academy of Sciences,Siberian Branch,3,Koptyug Ave.,Novosibirsk 630090,Russia [3]Geology&Geophysics Department,Novosibirsk State University,2 Pirogova Str.,Novosibirsk 630090,Russia [4]Diamond and Precious Metal Geology Institute,Russian Academy of Sciences,Siberian Branch,39,Lenina Ave.,Yakutsk 677000,Russia

出　　处：《Geoscience Frontiers》2022年第6期153-169,共17页地学前缘（英文版）

基　　金：the IGC State Assignment Project 0284-2021-0007;partially supported by the Russian Foundation for Basic Research (Grant No. 18-05-70014)。

摘　　要：Although the diamond potential of cratons is linked mainly to thick and depleted Archean lithospheric keels, there are examples of craton-edge locations and circum-cratonic Proterozoic terranes underlain by diamondiferous mantle. Here, we use the results of comprehensive major and trace-element studies of detrital garnets from diamond-rich Late Triassic(Carnian) sedimentary rocks in the northeastern Siberia to constrain the thermal and chemical state of the pre-Triassic mantle and its ability to sustain the diamond storage. The studied detrital mantle-derived garnets are dominated by low-to mediumCr lherzolitic(~45%) and low-Cr megacrystic(~39%) chemistries, with a significant proportion of eclogitic garnets(~11%), and only subordinate contribution from harzburgitic garnets(~5%) with variable CrOcontents(1.2–8.4 wt.%). Low-Cr megacrysts display uniform, “normal” rare-earth element(REE)patterns with no Eu/Eu* anomalies, systematic Zr and Ti enrichment(mainly within 2.5–5), which are evidence of their crystallization from deep metasomatic melts. Lherzolitic(G9) garnets exhibit normal or humped to MREE-depleted sinusoidal REE patterns and elevated Nd/Y(up to 0.33–0.41) and Zr/Y ratios(up to 7.62). Rare low-to high-Cr harzburgitic(G10) garnets have primarily “depleted”, sinusoidal REEpatterns, low Ti, Y and HREE, but vary significantly in Zr-Hf, Ti and MREE-HREE contents, Nd/Y(within 0.1–2.4) and Zr/Y(1.53–19.9) ratios. The observed trends of chemical enrichment from the most depleted,harzburgitic garnets towards lherzolitic(including high-Ti high-Cr G11-type) garnets and megacrysts result from either voluminous high-temperature metasomatism by plume-derived silicate melts or recurrent mobilization of less voluminous kimberlitic or related carbonated mantle melts, rather than the initially primitive, fertile nature of the Proterozoic SCLM. Calculated Ni-in-garnet temperatures(primarily within ~1150–1250 ℃) indicate their derivation from at least ~220 km thick Cr-undersaturated lithosphere at the

关 键 词：Siberian craton KIMBERLITE Diamond placers PERIDOTITES ECLOGITES MEGACRYSTS 

分 类 号：P619.241[天文地球—矿床学]