摘要
填隙矿物的流体包裹体研究与矿物的同位素地球化学研究可较好地揭示高放废物深地质处置库预选场址的深部热环境及古地下水热历史.中国高放废物深地质处置库第一个预选场深部花岗岩内填隙矿物的同位素、矿物学以及流体包裹体研究结果显示,甘肃北山地区花岗岩深部至少存在两种环境:浅部花岗岩(0～150m)填隙方解石的δ18O=-18.2‰～-15.8‰(PDB),δ13C=-9.5‰～-8.4‰(PDB),包裹体的均一温度(th)为140～160℃,包裹体的冰点温度为-2.5～-1.5℃,地下水可能以大气降水成因为主,且可能混合了盆地卤水并与花岗岩反应,形成温度、盐度(2%～5%,NaCleq)均较低的地下水;在350～550 m区段内(深部花岗岩),其δ18O值为-32.6‰～-17.6‰(PDB),δ13C值为-10.5‰～-6.2‰(PDB),流体包裹体的均一温度较其上部的稍高,为160～190℃,而其冰点温度则较低,为-4～-3.2℃(盐度5%～8%,NaCleq),地下水类型为大气降水与盆地古卤水的混合,以大气降水为主.石英的氧同位素组成和计算的古地下水氧同位素组成则进一步表明,花岗岩深部(350～550 m)也存在两种温度环境:较低温度(140～160℃)、较高盐度(5.5%～8%,NaCleq)的地下水;较高温度(220～240℃)、较低盐度(3%～5.5%,NaCleq)的地下水,其地下水类型为大气降水和与花岗岩平衡的卤水.
Fluid inclusion studies combined with isotope geochemistry of filling materials (calcite and quartz) from granite of the first pre-selected site for high-level radioactive waste deep geological repository in China can help us to better understand the past thermal and fluid history in granite environment. Isotopic, petrologic and fluid inclusion studies, undertaken as part of an investigation in the China radioactive waste deep geological disposal revealed that two major paleotemperature conditions were recorded by fracture fillings from deep granite: the fluid in the shallow part (from surface to 150 m) , precipitated crystalline calcite at 140-160℃ and salinity 2%- 5% (NaCleq), with δ 18O values of -18. 2‰--15. 8‰ (PDB) and δ 13C values of -9. 5‰--8. 4‰(PDB). Groundwater mainly originated from meteoric water penetration, mixed with basin brine, which interacted with granite body in equilibrium. In the deeper part (from 350 to 550 m) , both the fluid temperature(160-190℃) and salinity (5%-8% ,NaCleq) were higher, withδ 18O values of -32. 6‰--17. 6%0(PDB)and δ 13C values of -10. 5f3-- 6. 2‰ (PDB), suggesting a meteoric water origin with basin brine mixed. Oxygen isotopic composition of quartz and the calculated oxygen isotopic composition of paleo-groundwater further indicate that in the deep part of granite (350-550 m) there are also two temperature environments; the groundwater with lower temperature (140-160‰) and higher salinity (5. 5%-8% ,NaCleq), and that with higher temperature (220-240℃) and lower salinity (3%-5. 5%,NaCleq), suggesting an origin of meteoric water and brine balancced with granite.
出处
《地质论评》
CAS
CSCD
北大核心
2004年第5期548-553,共6页
Geological Review
基金
国家自然科学基金项目(编号40173031)中国高放废物深地质处置项目资助成果。
关键词
高放废物
流体包裹体
预选场
古温度
同位素地球化学
high-level radioactive waste
pre-selected site
groundwater
paleotemperature
isotope
