Petrological characteristics of lithospheric mantle beneath Nui Nua and Ba Ria areas, southern Vietnam
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Geosciences Journal
GJ
Petrological characteristics of lithospheric mantle beneath Nui Nua and Ba Ria areas, southern Vietnam Cong Nguyen and Youngwoo Kil* Department of Energy and Resources Engineering, Chonnam National University, Gwangju 61186, Republic of Korea
ABSTRACT: Spinel peridotites from the Nui Nua and Ba Ria volcanic suites of southern Vietnam were investigated to interpret mantle processes and geochemical evolution of the lithospheric mantle beneath southern Vietnam. Spinel peridotites from both study areas consist of lherzolites and harzburgites displaying porphyroclastic textures. The spinel peridotites may have experienced a low degree (1–13%) of fractional melting. The variation of light rare earth elements (LREEs) and other incompatible elements in clinopyroxenes indicates that most of the spinel peridotites have undergone silicate metasomatism. The spinel peridotite xenoliths of both areas originated at depths between 35 and 52 km with equilibrium temperatures ranging from 714–1211 °C (±15 °C). Correlations between Sr, Nd, and Pb isotopic compositions of the clinopyroxenes suggest that the spinel peridotites originated from mixing of depleted (DM) and enriched (EM2) mantle sources. The spinel peridotites from Nui Nua gave a Pb-Pb isochron age of 3.6 ± 0.3 Ga which suggests the formation time of lithospheric mantle beneath southern Vietnam due to initial melt extraction. Key words: Vietnam, lithospheric mantle, fractional melting, silicate metasomatism, isochron age Manuscript received September 3, 2019; Manuscript accepted May 13, 2020
1. INTRODUCTION As a part of the Indochina block, Vietnam represents a gap in the study of mantle xenoliths relative to other areas around Asia. Geological maps tend not to mention the presence of mantle xenoliths and geologists have typically overlooked them. Previous studies have described mantle xenoliths from the Central Highlands (Hoang and Flower, 1998; Hoang, 2005; Nguyen and Kil, 2019) and bodies found in the Song Ma ophiolite complex of northern Vietnam (Ngo et al., 2015). Mantle xenoliths occur sporadically in volcanic suites throughout southern Vietnam. These xenoliths consist primarily of spinel peridotites, and thus record physical-chemical states of the lithospheric mantle. As such, spinel peridotites can help characterize the *Corresponding author: Youngwoo Kil Department of Energy and Resources Engineering, Chonnam National University, Gwangju 61186, Republic of Korea Tel: +82-62-530-1731, Fax: +82-62-530-1729, E-mail: [email protected] Electronic supplementary material The online version of this article (https://doi.org/10.1007/s12303-0200017-8) contains supplementary material, which is available to authorized users.
©The Association of Korean Geoscience Societies and Springer 2020
lithospheric mantle and mantle processes affecting this region. This study describes petrography, major and trace element chemistry, and the formational history of spinel peridotites from Nui Nua and Ba Ria. Spinel peridotites within Cenozoic alkali basalt from Nui N
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