摘要
托云盆地晚白垩世—早第三纪碱性橄榄玄武岩Sr、Nd、Pb同位素组成表明 ,本区玄武岩以低Sr、Pb和相对高的Nd同位素值 (87Sr/ 86 Sr为 0 .70 3554～ 0 .70 3884 ;14 3Nd/ 14 4 Nd为0 .512 838～ 0 .512 90 4 ;2 0 6 Pb/ 2 0 4 Pb为 18.0 0 6 3～ 18.4 72 0 ;2 0 7Pb/ 2 0 4 Pb为 15.4 4 11～ 15.50 6 0 ;2 0 8Pb/ 2 0 4 Pb为 37.80 72～ 37.92 90 )为特征 ,相似于夏威夷的洋岛玄武岩。玄武质岩石的主要元素、微量元素和稀土元素特征进一步揭示 ,本区玄武质岩石起源于交代富集型地幔。这种富集型地幔经低度熔融形成原始岩浆 ,并在上升过程中经高位岩浆房的分离结晶作用 ,最终形成玄武质岩石。
The Tianshan Mountain is believed to be a typical intracontinental mountain belt; the Tianshan Mountain was formed during tectonic amalgamation of the Tarim and Tianshan block and the Siberian carton in Late Carboniferous-Permian period. A series of basaltic extrusive and intrusive units were emplaced primarily in Late Cretaceous-Plaeogene sedimentary rocks in Tuyon basin and its adjacent area, South Tianshan Mountain. Geochemical data of basalts show low Sr and Pb isotopic values and relative high Nd values ( 87 Sr/ 86 Sr= 0.703554 ～ 0.703884; 143 Nd/ 144 Nd =0.512838～0.512904; 206 Pb/ 204 Pb =18.0063～18.4720; 207 Pb/ 204 Pb = 15.4411 ～ 15.5060; 208 Pb/ 204 Pb =37.8072～37.9290). The data of major elements, trace elements and rare earth elements indicate that these basaltic rocks are similar to alkaline basalts of Hawaiian type oceanic silands. According to Nd/Sr isotopic ratios, the Tuyon basalts might have originated from low_grade melting of a source (mantle plume) similar to that beneath the Hawaiian Islands. In Tuyon basin and adjacent areas, several fields of Cenozoic alkaline basaltic magmatism may be related to the Cenozoic activity of mantle plumes.
出处
《岩石矿物学杂志》
CAS
CSCD
北大核心
2000年第2期131-139,共9页
Acta Petrologica et Mineralogica
基金
新疆305项目办公室基金(编号:96-915-07-03)
国土资源部国际合作科技司(编号:9501203)
国家自然科学重点基金(编号:F49734230)联合资助项目
关键词
南天山
玄武岩
地球化学
成因
south Tianshan Mountain
geochemical characteristics
alkalic basalts
genesis
