摘要
雷琼火山岩喷发时代<16Ma,以拉斑玄武岩为主,同位素与岩石化学证据具MORB与OIB过渡特征,为中国大陆最亏损的地幔端元并受到三水盆地型古俯冲带地幔源的影响。^(143)Nd/^(144)Nd-^(147)Sm/^(144)Nd相关表明经历了前寒武纪亏损(>570Ma),古生代富集(500—150Ma)以及中生代亏损三个发展阶段。Pb-Pb等时线显示出近于3.6Ga地幔事件。地球化学与地质证据表明该区火山喷发可能与四会-吴川和红河-金沙江两条构造线的交汇形成深的地幔通道有关。
The Cenozoic volcanics in the Leiqiong area, South China, are mainly tholeiites, giving eruption ages lower than 16Ma. Their petrochemistry is intermediate between MORB and OIB. Nd, Sr and Pb isotopic compositions are in the ranges 0 51274-0.51304, 0.7031-0.7040 and 18.14-18.69, respectively. The Nd-Sr-Pb isotopic correlations also show MOR3-OIB features, which represent the most depleted mantle region beneath the East China Continent. A few samp-les have higher 87Sr/86Sr ratios( > 0.7043), indicating the influence of the ancient mantle source like the Shanshui Basin. The plot of 143Nd/144Nd v.s. 147Sm/144Nd revels a history of three-stage evolution: depletion in Precambrian (>570Ma), enrichment in Paleozoic (500-150Ma) and depletion again since Mesozoic. The Pb-Pb isochron yielded information on a mantle event of about 3.6 Ga. It is indicated from geochemical and geologic evidence that the volcanism in this area is associated with the junction between the tectonic lines of Sihui-Wuchuan and Jinsa-Red River, which serves as a channelway for magmas from the deep mantle.
出处
《地球化学》
CAS
CSCD
北大核心
1989年第3期193-201,共9页
Geochimica
基金
国家科学基金(4870186
4860109)
