摘要
胶东金矿的早晚两期成矿系列中,岩浆成因或在岩浆期即有天然水和表生矿质加入的矿床,δ ̄(34)S值均有自早而晚依次降低的规律。为重熔岩浆分异成矿理论和成矿系列的建立提供了重要证据。焦家式和某些晚期矿床,在形成矿液后有表生硫加入,扰乱了这一规律性。胶东群中的硫同位素没有达到均匀化,副变质岩偏重,而斜长角闪岩偏轻,接近陨石硫值,是近似原始岩浆的产物。
The endogenic gold deposits in Jiaodong area might be assigned tO twometallogenic epochs:principal(late Jurassic) epoch and accompanying(EarlyCretaceous)epoch,resulting both from the differentiation and evolution of a- natectic magma,In each epoch of the metallongenic serries,δ ̄(34)S values tend to decrease gradually from e arly to late,while things are quite the opposite for δ ̄(18)O values,The anatectic magma formed in the principal mineralization epoch occurred in larger depth,and its δ ̄(34)S values are somewhat high,varying from 8.9‰of the granite through 6.9‰ of the intermediate-basic dikes to 6.7‰ of the gold deposits,In contrast,the anatectic magma formed in the accompanying mineralization epoch occurred in shallower place,and the process of its forma- tion was characterized by the participation of meteoric water and exogenic ore substances;as a result,its δ ̄(34)S values are slightly lower,varying from6.6‰ ofthe early granodiorite through 2.4‰ of the intermediate-basic dikes to-2.6‰ of the ore deposits,These data demonstrate that sulfur isotope fraction mainly follows the principle of thermodynamic effect,whereas oxygen isotope fractio- nation is chiefly restricted by the theorem of kinetic energy.All this has pro- vided the important basis for the establishment of the metallogenic theory of differentiation and evolution of anatectic magma and the metallogenic series. The Jiaojia type gold deposits occur in large-size and gently-dipping tecto-nic shatter zones where large quantities of meteoric water and exogenic ore substances are stored.Once connceting with ore magma,the meteoric water and exogenic ore substanca would particicipate in the ore-forming process,After theore magma was trapped under great confining pressure, exogenic sulfur would be mixed and exchanged with magma sulfur in a reducing environment.The equilibrium temperature between galena and sphalerite would remain stable at the end of the principal ore-forming stage. Hence the δ ̄(34)S values of the Jiaojia type deposits obviously deviate toward the positive side. The participation of exogenic sulfur to the ore-forming process has confused the regularity of sulfur isotope evolution.
出处
《矿床地质》
CAS
CSCD
北大核心
1994年第1期75-87,共13页
Mineral Deposits
关键词
硫同位素
成矿系列
金矿床
sulfur isotope,metallogenic series,supergene ore material,magmatic differentiation, anatectic magma