High-Mg lavas from the Dariganga volcanic field in the South-Eastern Mongolia: petrogenetic model of magmatism at the asthenosphere-lithosphere boundary

Abstract

It is revealed that highMg lavas (MgO=11.0-15.8 wt. %) are spatially controlled by linear zones extending for more than 90 km and demonstrate chemically distinct differences from moderatelyMg compositions (MgO=3.0-11.0 wt. %), which occupy the isometric area of the Dariganga volcanic field. From the major and traceelement data on the rocks in the field under study, we have justified a petrogenetic mode of the uniform onelevel mantle magmatism. Our model differs from the contrasting magmatism model of the processes that developed at two levels beneath the Hannuoba volcanic field. Based on tomography images showing the East Mongolian local lowvelocity anomaly in the upper mantle, we suggest that magma tism of Type 1 occurred in the mantle sources at the asthenosphere-lithosphere boundary and the underlying asthenosphere as a reflection of a relatively weak mantle flow that may have ascended from a depth of ~250 km. Magmatism of Type 2 occurred in the isolated sources of the sublithospheric mantle and the asthenosphere-lithosphere boundary as an evidence on the initially strong mantle flow that may have ascended from a depth of ~410 km. Аннотация: Установлен пространственный контроль высокомагнезиальных вулканических пород (MgO=11.0-15.8 мас. %) линейными зонами протяженностью более 90 км и резкие отличия их химического состава от умеренно магнезиальных (MgO=3.0-11.0 мас. %) пород, занимающих всю изометричную территорию вулканического поля Дариганга. При сравнительном анализе петрогенных и малых элементов пород этого поля обоснована петрогенети ческая модель мантийного магматизма одного глубинного уровня, в отличие от модели контрастных магматических процессов, проявленных на двух глубинных уровнях под вулканическим полем Ханнуоба. С учетом томографиче

Mid-Miocene thermal impact on the lithosphere by sub-lithospheric convective mantle material: Transition from high- to moderate-Mg magmatism beneath Vitim Plateau, Siberia

“…They both can be interpreted in connection with increasing degree of partial melting at elevated temperatures. From model calculations by Chuvashova et al (2012), it was inferred that the Hannuoba evolved alkali olivine basalts were derived by 2-5% partial melting of a source that had 4.5-6.0% of garnet. These parameters are close to those of a source for high-Mg rocks from the Bereya volcanic center.…”

Mid-Miocene sequences of high- and moderate-Mg volcanic rocks in Vitim Plateau, Southern Siberia: Impact of a sub-lithospheric convective material on the lithosphere

“…Этим извержениям предшествовали и за ними следовали извержения низко-Mg базальтов, слагающих вулканические толщи с датировками в интервалах, соответственно, 18.1-17.6 и 13-12 млн лет [Rasskazov et al, 2003b;. Подобным образом небольшие тела высоко-Mg пород и объемные массивы пород низко-Mg состава соотносятся на Витимском и Дариганском вулканических полях [Aschepkov, 1991;Aschepkov et al, 2003;Chuvashova et al, 2012Chuvashova et al, , 2015.…”