江西武功山中生代变质核杂岩的花岗岩类Nd-Sr同位素研究  

Nd-Sr ISOTOPIC COMPOSITIONS OF GRANITIC ROCKS OF THE MESOZOIC METAMORPHIC CORE COMPLEX IN THE WUGONGSHAN AREA, JIANGXI PROVINCE

作　　者：舒良树[1] 王德滋[1] 沈渭洲[1] 

机构地区：[1]南京大学地球科学系,南京大学成矿作用研究国家重点实验室,江苏南京210093

出　　处：《南京大学学报（自然科学版）》2000年第3期306-311,共6页Journal of Nanjing University（Natural Science）

基　　金：国家自然科学基金重点资助项目!(批准号 :496 32 0 80 )

摘　　要：采自江西中生代伸展构造区武功山变质核杂岩的 7组花岗岩类的Nd -Sr同位素组成表明 ,它们具有两组ISr值 :加里东期山庄花岗闪长质岩体ISr=0 .70 6 6 1;中生代武功山区花岗岩类ISr =0 .70 981～ 0 .716 96 ,平均 0 .71381.七组样品都表现为低的εNd 值 :- 13.7到 - 10 .5,平均- 12 .0 .Nd模式年龄古老 :1835～ 2 12 8Ma .在εNd-t图上 ,所有数据均落在江西中部中元古代变质沉积岩的Sm -Nd演化区内 ,远离球粒陨石地幔演化线 .结合岩石化学上的高钾、过铝以及岩体含有硅线石矿物等特征 ,认为武功山变质核杂岩的花岗岩类是由与元古代变质沉积岩相似的大陆地壳岩石通过部分熔融而形成的 .This paper studies the seven groups of Nd-Sr isotopic compositions from granitic bodies of the Mesozoic metamorphic core complex in the Wugongshan area, Jiangxi Province. Results suggest that the 2 groups of I Sr value exist in the bodies, that is, Caledonian granitic diorite in Shanzhuang has the I Sr =0.706?61 and Mesozoic granitic rocks have the I Sr =0.709?81-0.716?96, average value 0.713?81. Seven samples display lower ε Nd values, from -13.7 to -10.5, average value is -12.0. The Nd model age of these bodies is older, from 1?825?Ma to 2?128?Ma. On the ε Nd -T diagram, all ε Nd data drop in the Sm-Nd evolutionary field of the Middle Proterozoic meta sedimentary rocks in the central Jiangxi and are far away from the mentle evolutionary line of chrondrite. The granitoids in the Wugongshan are characterized by higher K 2O and Al 2O 3 contents and the marked mineral of sillimanite. We conclude that granitoids in the Wugongshan metamorphic core complex were formed by a partial melting of crustal rocks similar to the Proterozoic meta-sedimentary rocks in the Central Jiangxi.

关 键 词：花岗岩类 中生代 变质核杂岩 江西 钕-锶同位素 

分 类 号：P588.3[天文地球—岩石学] P588.121[天文地球—地质学]