SPINEL PERIDOTITE XENOLITHS FROM THE ATSAGIN-DUSH VOLCANO, DARIGANGA LAVA PLATEAU, MONGOLIA: A RECORD OF PARTIAL MELTING AND CRYPTIC METASOMATISM IN THE UPPER MANTLE
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dc.contributor.author | Wiechert U. | |
dc.contributor.author | Wedepohl K.H. | |
dc.contributor.author | Ionov D.A. | |
dc.date.accessioned | 2020-12-24T03:38:07Z | |
dc.date.available | 2020-12-24T03:38:07Z | |
dc.date.issued | 1997 | |
dc.identifier | https://elibrary.ru/item.asp?id=13703862 | |
dc.identifier.citation | Contributions to Mineralogy and Petrology, 1997, , 4, 345-364 | |
dc.identifier.uri | https://repository.geologyscience.ru/handle/123456789/21227 | |
dc.description.abstract | Spinel peridotite xenoliths from the Atsagin-Dush volcanic centre, SE Mongolia range from fertile lherzolites to clinopyroxene(cpx)-bearing harzburgites. The cpx-poor peridotites typically contain interstitial fine-grained material and silicate glass and abundant fluid inclusions in minerals, some have large vesicular melt pockets that apparently formed after primary clinopyroxene and spinel. No volatile-bearing minerals (amphibole, phlogopite, apatite, carbonate) have been found in any of the xenoliths. Fifteen peridotite xenoliths have been analysed for major and trace elements; whole-rock Sr isotope compositions and O isotope composition of all minerals were determined for 13 xenoliths. Trace element composition and Sr-Nd isotope compositions were also determined in 11 clinopyroxene and melt pocket separates. Regular variations of major and moderately incompatible trace elements (e.g. heavy-rare-earth elements) in the peridotite series are consistent with its formation as a result of variable degrees of melt extraction from a fertile lherzolite protolith. The Nd isotope compositions of LREE (light-rare-earth elements)-depleted clinopyroxenes indicate an old (≥ 1 billion years) depletion event. Clinopyroxene-rich lherzolites are commonly depleted in LREE and other incompatible trace elements whereas cpx-poor peridotites show metasomatic enrichment that can be related to the abundance of fine-grained interstitial material, glass and fluid inclusions in minerals. The absence of hydrous minerals, ubiquitous CO2-rich microinclusions in the enriched samples and negative anomalies of Nb, Hf, Zr, and Ti in primitive mantle-normalized trace element patterns of whole rocks and clinopyroxenes indicate that carbonate melts may have been responsible for the metasomatic enrichment. Low Cu and S contents and high δ34S values in whole-rock peridotites could be explained by interaction with oxidized fluids that may have been derived from subducted oceanic crust. The Sr-Nd isotope compositions of LREE-depleted clinopyroxenes plot either in the MORB (mid-ocean-ridge basalt) field or to the right of the mantle array, the latter may be due to enrichment in radiogenic Sr. The LREE-enriched clinopyroxenes and melt pockets plot in the ocean island-basalt field and have Sr-Nd isotope signatures consistent with derivation from a mixture of the DMM (depleted MORB mantle) and EM (enriched mantle) II sources. | |
dc.title | SPINEL PERIDOTITE XENOLITHS FROM THE ATSAGIN-DUSH VOLCANO, DARIGANGA LAVA PLATEAU, MONGOLIA: A RECORD OF PARTIAL MELTING AND CRYPTIC METASOMATISM IN THE UPPER MANTLE | |
dc.type | Статья |
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