Introduction
Overview
Mantle xenoliths, also known as mantle nodules or mantle inclusions, have been extensively studied for centuries due to their valuable mineralogical and chemical information, which helps geologists understand the characteristics of the Earth's mantle beneath specific regions Unlike mantle lithologies derived from alpine-type massifs, which can be altered during transportation to the crust, mantle xenoliths primarily retain the properties of the mantle These xenoliths are typically found as peridotites within three main magma types: alkali basalts, lamprophyres, and kimberlites Peridotites are present in both oceanic and continental tectonic settings, with continental peridotites being more prevalent and categorized into craton and off-craton types based on crustal age Seismological studies further reveal that the Earth's lithospheric mantle is predominantly composed of peridotites.
Spinel peridotites, frequently discovered in alkali basalts from off-craton regions, serve as a valuable resource for enhancing our understanding of the lithospheric mantle These peridotites reveal crucial petrographical, physical, and chemical characteristics, as well as the mantle processes that have influenced them The two primary processes impacting the lithospheric mantle are the depletion of peridotites through partial melting and magma extraction, and the enrichment of peridotites via metasomatism Additionally, the co-existing minerals within peridotites are instrumental in determining equilibrium temperatures.
Peridotite xenoliths, captured by alkali basalts, provide valuable insights into the pressures and depths of the Earth's mantle The radiogenic isotope compositions of these peridotites are essential for understanding mantle processes and help to determine the origin, age, and evolution of the lithospheric mantle (Menzies et al., 1987; Pearson and Nowell, 2002; Tatsumoto et al., 1992).
Over 3,500 localities of mantle xenoliths have been identified globally, showcasing diverse characteristics and heterogeneities in lithospheric mantle components (Pearson et al., 2003; Nixon, 1987) However, the mantle xenoliths from Vietnam, situated on the Indochina Block, remain underexplored, with limited references in previous studies by Hoang (2005), Hoang and Flower (1998), and Nguyen and Kil (2019), which primarily focused on the Pleiku and Buon Ma Thuot basalt plateaus Consequently, a comprehensive investigation of mantle xenoliths across the Central Highlands of Vietnam (CSVN) is essential for a deeper understanding of their properties and significance.
This study investigates spinel peridotites found in alkali basalts from seven volcanic suites to reveal the characteristics of the lithospheric mantle beneath the CSVN, Indochina Block It systematically examines petrography, mineral chemistries, and radiogenic isotope compositions (Sr, Nd, Pb), along with equilibrium temperatures and extraction depths of the lithospheric mantle The findings provide a clearer interpretation of the processes and evolution of the lithospheric mantle, enhancing our understanding of this extensive region beneath the Indochina Block Additionally, the research clarifies the similarities and differences between the lithospheric mantle of the Indochina Block and the South China Block.
General geology
Vietnam's geological history is marked by two significant tectonic events The first, the Indosinian orogeny, occurred during the Triassic period (250-240 million years ago) and was caused by the collision of the Indochina Block with the South China Block, alongside the convergence of the Indochina Block with Gondwana-derived continental blocks The second major event is the India-Eurasia collision, which took place in the Paleogene period (50-55 million years ago), leading to widespread intraplate basalt eruptions across eastern and southeastern Asia, as well as western Pacific marginal basins These basalts exhibit pull-apart structures influenced by strike-slip and normal faulting, which have significantly shaped the basalt centers of eastern Indochina.
The Central Highlands of Vietnam (CSVN) features extensive basalt coverage, spanning approximately 23,000 km² and reaching thicknesses of several hundred meters (Hoang and Flower, 1998) Significant volcanic activity occurred in various centers during specific geological intervals, including Da Lat (17.6-7.9 Ma), Phuoc Long (