地质科学2013，Vol.48Issue(2)：449-467,19.DOI:10.3969/j.issn.0563-5020.2013.02.009
青藏高原北部白榴碧玄岩年代学及地球化学研究
Geochronology and geochemistry of the high magnesium and high potassium ultrabasic leucite basanite in northern Tibetan Plateau
摘要
Abstract
The high magnesium and high potassium ultrabasic leucite basanites were first found in the Silver Mountain region of northern Tibet. Leucite basanites are located in the south of A'nyemaqen-Kunlun-Muztag suture zone, covering an area of about 0. 2 km2 and the age of the volcano eruption is about 5-4 Ma dated by Ar-Ar method. The phenocrysts are mainly composed of olivine ( 10% ~ 12% ) , leucite ( 21% ~ 27% ) , nepheline ( 13% ~ 16% ) and diopside(29% ~ 31% ) , and the groundmass( ~ 30% ) is composed of fine grain of diopside, biotite, Fe-Ti oxide and glass. The composition of the olivine phenocrysts are Fo74-87 Fa13-26 , without obvious kink band, which suggests that the olivine phenocrysts were crystallized from magma rather than xenoliths captured from mantle. The estimated crystallization temperature ranges from 1 226 X, to 1 234 t. Leucite basanites contain SiO2<45% ,MgO>10% , Na2O + K2O>8% ,higher Mg (68. 84 -70. 80) ,high concentration of some compatible elements,such as Cr( 149×10-6 - 156 × 10-6) and Ni ( 138 ×10-6 - 151 ×10-6). The ratios of 87Sr/6 Sr ( -0.708 6) and 143Nd/144Nd( -0.512 4) are within a typical EMU source area. Therefore, we argued that these ultrabasic leucite basanites were originated from the partial melting of the mantle rocks at the top of the asthenosphere, and probably contaminated by the subducted crust material.关键词
高镁—高钾质/白榴碧玄岩/上新世/软流圈/青藏高原Key words
High magnesium and high potassium, Leucite basanite, Pliocene,Asthenosphere, Tibetan Plateau分类
天文与地球科学引用本文复制引用
杨迪,丁林..青藏高原北部白榴碧玄岩年代学及地球化学研究[J].地质科学,2013,48(2):449-467,19.基金项目
中国科学院资环局国际合作项目(编号:KZCX2-YW-GJ05)、中国科学院战略性先导科技专项(编号:XDB05010400)和科技部"973"项目(编号:2011CB403101)资助. （编号:KZCX2-YW-GJ05）
