Petrochemical study of the Jingpohu Holocene alkali basaltic rocks, northeastern China.

Abstract

Holocene volcanoes in the Jingpohu region are situated in the "Crater Forest" and "Frog Pool" areas along the northwest side of Jingpohu Lake, northeastern China. Dating of three charcoal samples from the first and second volcanic cycles shows that the ages of the first and second cycles are 3430~3490 and 2470 years respectively. The lavas from the Jingpohu area consist of basanites (BSN), alkali olivine basalts (AOB) and tephrites (TP). Crystal fractionation models are consistent with the generation of AOB and TP from a basanitic parent. Minor fractionation of olivine, augite, magnetite and Cr-spinel is required to produce AOB compositions whereas the generation of TP requires extensive fractionation of kaersutite, phlogopite and anorthoclase with minor olivine, augite, magnetite and leucite. The presence of kaersutite, phlogopite and anorthoclase megacrysts and mantle xenoliths suggest a fractionation history occurring at high pressure in the mantle. Although all basaltic rocks contain many granitic xenoliths, their geochemical characteristics show that they have not undergone any contamination of upper crust en route to the surface, but some alkali basalts were suffered from the contamination of lower crust. Relatively unradiogenic isotope ratio (compared with Bulk Earth), steep chondrite-normalized REE patterns and strong incompatible element enriched patterns suggest that the magmas are derived from a mixture of an incompatible element depleted anhydrous lherzolite asthenospheric mantle source and an enriched, amphibole-phologite-(apatite-)bearing lherzolite continental lithospheric mantle source. We propose that the basanites are the products of very low degree partial melts (<1%) of this source under high extension strength.

Earth Surface Processes and Environmental Changes in East Asia

“…7.1). Jingpo Lake is surrounded by low mountains, topography of the catchment is dominated by hilly plains with a small relative elevation, and with the major rock types include granite, alkali olivine basalts, basanites and tephrites (Zhang et al 2002). The lake has a surface area of 92 km 2 , with a maximum water depth of 48 m and an average depth of 12.9 m. The length of Jingpo Lake from north to south is 45 km, and the widest distance from east to west is only 6 km (Wang and Dou 1998).…”

“…Therefore, systematic study of the lava-dammed lakes histories, particularly the formation age and evolutional processes, is essential to understanding the occurrence of natural disasters, and consequently, in developing and applying adequate strategies for prevention and mitigation of natural disasters and loss of life and property (Alcántara-Ayala 2002). According to 14 C dating of carbonized wood and charcoal samples, however, some other scholars suggested that Jingpo Lake formed about 5,500-4,400 yr BP (Zhang et al 2002;Fan et al 2003Fan et al , 2005Chuvashova et al 2007;Jia et al 2013). The Jingpo volcanoes is situated in the eastern part of the eastwest trending Central Asian Orogenic Belt (CAOB) and in the western part of the Dunhua-Mishan Fault (Davis and Marc 2001;Buchan et al 2002;Yan and Zhao 2008).…”

Mantle sources of the Cenozoic volcanic rocks of East Asia: Derivatives of slabs, the sublithospheric convection, and the lithosphere

“…The last eruptions in this area occurred in 1720-1721 at the Laoheishan and Huoshaoshan vol canoes of the Wudalianchi field [34,35,60]. The melts contained a common component with ( 87 Sr/ 86 Sr) 0 = 0.7052 [12,24].…”

Sr-Nd-Pb isotopic compositions of submarine alkali basalts recovered from the South Korea Plateau, East Sea

“…Several petrological and geochemical studies were carried out for these alkali rocks to address their magma sources and petrogenesis and to discuss deep dynamic processes possibly associated with lithosphere-asthenosphere interaction and lithospheric evoultion Kil and Lee, 2005;Choi et al, 2005;Park et al, 2005;Choi et al, 2006;Shin et al, 2006). These rocks all show oceanic island basalt (OIB)-like geochemical characteristics, similar to those of Cenozoic alkaline volcanic products in eastern China (Tatsumoto et al, 1992;Liu, et al, 1994;Liu et al, 2001;Zhang et al, 2002;Liu et al, 2004), East Sea (Japan Sea) region and SW Japan (Tatsumoto and Nakamura, 1991;Uto et al, 2004;Hoang and Uto, 2006). They have been interpreted as the products derived from convectively upwelling asthenosphere and/or thermally activated lithospheric mantle during continental extension (e.g., Uto et al, 2004;Choi et al, 2006).…”