摘要
Nd- Sr- Pb同位素体系对三江地区古特提斯火山岩的示踪结果表明 ,古特提斯时期三江地区存在亏损和近原始两种地幔储库。亏损地幔的 ISr=0 .70 4 1～ 0 .70 77,εNd(t)=+2 .87～ +7.2 4 ;近原始地幔的 ISr=0 .70 39～ 0 .70 79,εNd(t) =- 0 .96～ +5 .4 1。它们均属南半球地幔域。亏损地幔和近原始地幔分别是三江地区 MORB和 OIB的源区物质。金沙江洋内弧火山岩继承了 MORB的源区物质 ,ISr=0 .70 6 0～ 0 .70 6 6 ,εNd(t) =+6 .2 4～ +7.5 4 ;碰撞弧火山岩的源区物质是陆壳重融物 ,ISr=0 .72 0 3～ 0 .72 35 ,εNd(t) =- 8.80～ - 10 .76 ;滞后弧火山岩的源区物质是陆壳重融物与少量地幔柱熔融物的混合物 ,ISr=0 .70 77～ 0 .70 99,εNd(t) =- 2 .5 6～ - 9.93。澜沧江陆缘弧火山岩的源区物质是洋壳、大洋沉积物和陆壳物质的混合物 ,ISr=0 .70 5 2～ 0 .7111,εNd(t) =+0 .6 1～ - 7.2 6。Sr- Pb同位素联合示踪还表明 ,三江地区存在 Dupal异常 ,其ΔSr>4 0 ,Δ 8/ 4 >6 0和Δ7/ 4 >7。
Nd Sr Pb isotope systematics tracing on Paleo Tethyan volcanic rocks in the Sanjiang(Jinshajiang Lancangjiang Nujiang) shows that there exist depleted and primitive mantle reservoirs in the Sanjiang area during the Paleo Tethyan period. The I Sr of depleted mantle ranges from 0.704 1 to 0.707 7 and ε Nd (t) from +2.87 to +7.24, while the I Sr of primitive mantle from 0.7039 to 0.7079 and ε Nd (t) from -0.96 to +5.41. They belong to mantle reservoirs of the southern hemisphere. The MORB and OIB of the Sanjiang area were generated from the depleted mantle and the primitive mantle respectively. The source material of the Jinshajiang oceanic island volcanic rocks (I Sr =0.706 0~0.706 6 and ε Nd (t)=+6.24^+7.54) inherited the source material of the MORB. Collision type arc volcanic rocks(I Sr =0.720 3~0.723 5 and ε Nd (t)= -8.80 ^-10.76) were originated from the continental crust. Post collision type arc volcanic rocks (I Sr =0.707 7~0.709 9 and ε Nd (t) = -2.56^-9.93) came from mantle plume magma which was contaminated by continental crust. The source materials of the Lancangjiang continental marginal arc volcanic rocks (I Sr =0.705 2~0.711 1 and ε Nd (t)=+0.61^-7.26) was a mixture of oceanic crust, oceanic sediments and continental crust. Sr Pb isotope tracing shows that there exists Dupal anomaly in the Sanjiang area (ΔSr>40,Δ8/4>60 and Δ7/4>7).
出处
《矿物岩石》
CAS
CSCD
北大核心
2003年第1期55-60,共6页
Mineralogy and Petrology
基金
中国博士后科学基金资助项目
国土资源部"九五"科技攻关项目 (No.95 -0 2 -0 0 1-0 2 )
国家科委"九五"科技攻关项目 (No.96-914 -0 1-0 3 )
