Holocene volcanic rocks in Jingbo Lake region --Diversity of magmatism  

作　　者：FAN Qicheng SUN Qian LI Ni WANG Tuanhua 

机构地区：[1]Institute of Geology, China Seismological Bureau, Beijing 100029, China

出　　处：《Progress in Natural Science:Materials International》2006年第1期65-71,共7页自然科学进展·国际材料（英文版）

基　　金：Supported by National Natural Science Foundation of China (Grant No. 40372044) and the Ministry of Science and Technology of China (2002DIA20009)

摘　　要：During the time from 5500 a to 5200 a BP more than 10 Holocene volcanoes in Jingbo Lake region erupted and the volcanic rocks covered an area of about 500 km^2. Holocene volcanic rocks in Jingbo Lake region belong to the potassium-rich rocks and contain three rock types： trachybasahs, hasanites and phonotephrites. Various types of magmatism formed in a small area and in a short period of time came from partial melting of potassically metasomatised lithospheric mantle. The diversity of magmatism can be explained by that Jingbo Lake is situated in the back-arc extensional region of East Asian continent subducted by the Pacific Ocean, and potassic fluid derived from mantle wedge or dehydration of subducted slab can result in a high heterogeneity of the mantle beneath this region. Based on the pressure estimation of clinopyroxene megacrysts, we estimate that phonotephrite magma fractionally crystallize at ca. 52-54 km down the earth.During the time from 5500 a to 5200 a BP more than 10 Holocene volcanoes in Jingbo Lake region erupted and the volcanic rocks covered an area of about 500 km2. Holocene volcanic rocks in Jingbo Lake region belong to the potassium-rich rocks and contain three rock types: trachybasalts, basanites and phonotephrites. Various types of magmatism formed in a small area and in a short period of time came from partial melting of potassically-metasomatised lithospheric mantle. The diversity of magmatism can be explained by that Jingbo Lake is situated in the back-arc extensional region of East Asian continent subducted by the Pacific Ocean, and potassic fluid derived from mantle wedge or dehydration of subducted slab can result in a high heterogeneity of the mantle beneath this region. Based on the pressure estimation of clinopyroxene megacrysts, we estimate that phonotephrite magma fractionally crystallize at ca . 52-54 km down the earth.

关 键 词：magma diversity mantle heterogeneity Holocene volcano Jingbo Lake 

分 类 号：P588.1[天文地球—岩石学]