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Title: | Petrology, geochemistry, and Sr, Nd isotopes of mantle xenolith in Nghia Dan alkaline basalt (West Nghe An): implications for lithospheric mantle characteristics beneath the region |
Authors: | Tran, Thi Huong Nguyen, Hoang |
Keywords: | Nghia Dan Alkaline basalt Mantle xenolith Spinel-lherzolite Clinopyroxene |
Issue Date: | 2018 |
Series/Report no.: | Vietnam Journal of Earth Sciences;No.03, Vol.40 .- P.207–227 |
Abstract: | Study of petrological and geochemical characteristics of mantle peridotite xenoliths in Pliocene alkaline basalt in Nghia Dan (West Nghe An) was carried out. Rock-forming clinopyroxenes, the major trace element containers, were separated from the xenoliths to analyze for major, trace element and Sr-Nd isotopic compositions. The data were interpreted for source geochemical characteristic and geodynamic processes of the lithospheric mantle beneath the region. The peridotite xenoliths being mostly spinel-lherzolites in composition, are residual entities having been pro¬duced following partial melting events of ultramafic rocks in the asthenosphere. They are depleted in trace clement abundance and Sr-Nd isotopic composition. Some are even more depleted as compared to mid-ocean ridge mantle xenoliths. Modelled calculation based on trace element abundances and their corresponding solid/liquid distribution coefficients showed that the Nghia Dan mantle xenoliths may be produced of melting degrees from 8 to 12%. Applying various methods for two-pyroxene temperature - pressure estimates, the Nghia Dan mantle xenoliths show ranges of crystallization temperature and pressure, respectively, of 1010-1044°C and 13-14.2 kbar, roughly a bout 43km. A geotherm constructed for the mantle xenoliths showed a higher geothermal gradient as compared to that of in the western Highlands (Vietnam) and a conductive model, implying a thermal perturbation under the region. The calculated Sm-Nd model ages for the clinopyroxenes yielded 127 and 122 Ma. If the age is meaningful it suggests that there was a major geodynamic process occurred beneath Western Nghe An in the middle-Early Cretaceous that was large enough to cause pcrturbalion in the evolutional trend of the Sm-Nd isotopic system. |
URI: | https://dspace.ctu.edu.vn/jspui/handle/123456789/47473 |
ISSN: | 0866-7187 |
Appears in Collections: | Vietnam journal of Earth sciences |
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