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大别山地区榴辉岩全岩的3He/4 He值分布在0 .0 13×10 - 6 ～0 .76 0×10 - 6 之间,平均0 .2 0 0×10 - 6 ,榴辉岩中石榴子石单矿物的3He/4 He值与其全岩的3He/4 He值基本一致。在3He—4 He分布图上榴辉岩的氦同位素数据点远离地幔氦的分布范围,而位于大气氦与地壳氦的过渡部位。采用真空压碎方法对榴辉岩中石榴子石和绿辉石的氦同位素组成进行了分析,也未找到地幔氦的明显踪迹。结合大别—苏鲁地区榴辉岩中极低的δ1 8O值、εNd(0 )值等地球化学特征,提出大别—苏鲁地区超高压变质榴辉岩可能是在地壳中形成的,并未曾俯冲至10 0多千米的地幔深度。榴辉岩的3He/4 He值与围岩类型密切相关,榴辉岩的δ1 8O值与围岩的δ1 8O值同步变化,以及含柯石英大理岩、片麻岩和硬玉石英岩等非基性超高压变质岩和脉状榴辉岩的发现,均证明榴辉岩与其围岩一起经历了超高压变质过程,榴辉岩及其围岩在变质过程中未发生明显的位移,即榴辉岩是原地成因的。
The 3He / 4 He values of eclogites in the Dabie Mountain ranged from0.013 × 10-6to0.676 × 10-6, with an average of0.2 × 10-6 The 3He / 4 He value of the garnet single mineral is basically the same as the 3He / 4 He value of the whole rock. The helium isotope data of the eclogite on the 3He-4 He distribution map are far from the distribution of the helium in the mantle and are located at the transition between atmospheric helium and the crustal helium. The helium isotopic composition of garnet and omphacite in eclogites was analyzed by vacuum crushing method, and no obvious trace of helium in the mantle was found. Combined with the extremely low δ180 values and εNd (0) values in the eclogites of the Dabie-Sulu area, it is suggested that the UHP metamorphic eclogite in the Dabie-Sulu area may be formed in the crust The depth of the mantle has not been subducted to more than 10 km. The 3He / 4 He values of eclogites are closely related to the surrounding rock types. The δ18O values of the eclogites synchronously change with the δ18O values of the surrounding rocks, and non-radicals such as Coke quartz marble, gneiss and jade quartzite The discovery of EHP metamorphic rocks and vein-shaped eclogites both proved that the eclogites experienced the UHP metamorphism along with their surrounding rocks. The eclogite and its surrounding rocks did not show obvious displacement in the metamorphism, ie, the eclogitic Rock is in situ.