摘要
对德兴铜矿区的铜厂斑岩铜矿中出现的岩浆成因和热液成因磷灰石进行了对比研究。在铜厂,除含矿斑岩体中含有磷灰石以外,成矿早期蚀变(钾化)与主矿化期蚀变(石英-绿泥石-绢云母化)也形成了磷灰石。电子探针分析结果表明三期磷灰石成分差异显著,岩浆期磷灰石的主要特征是富S和Si,钾化期磷灰石的主要特征是富Mn和Fe,主矿化期磷灰石与早期磷灰石的主要差别在于其较高的S含量、F含量和较低的Cl含量;岩浆期、钾化期和主矿化期磷灰石的Cl/F比值依次降低,这反映了流体和岩浆Cl/F比值的演化趋势。岩浆Cl/F比值的降低可能由岩浆的析气作用以及Cl和F在岩浆和流体中的分配系数不同所致。S在岩浆期磷灰石和主矿化期磷灰石中均作为P的替位阳离子存在,但在两期磷灰石中替位机制不同,P-S替位的电荷平衡离子分别为Si和Na。在三期磷灰石中,主矿化期磷灰石S含量最高,而Cl含量显著低于岩浆期和钾化期磷灰石,这表明在主矿化期,Cu-S配合物可能是比Cu-Cl配合物更重要的金属搬运形式。
Thais paper reports electron microprobe analysis results of apatite from the Tongchang porphyry copper deposit. Apatite of different features is identified in three generations of mineral assemblages at Tongchang, namely, magmatic stage, potassic stage, and phyllic stage （main mineralization stage）. Magmatic apatite is characterized by its high Si and S contents; potassic-stage apatite is characterized by high Fe and Mn contents, which is likely the result of decomposition of Fe- and Mn- bearing minerals during potassic alteration; as to the main mineralization stage apatite, high S and F contents are its obvious characteristics. Relationships between different continents of apatite imply SSiP_2and NaSCa-1 P1 1ate the substitution form of S in the magmatic and main mineralization stage apatite, respectively. Compositional study of apatite indicates H20/HF and HC1/HF ratios of magma decrease from the early to the late stage, which may be caused by combination of fractional crystallization of OH-beating minerals and degassing-evolved Cl-loss. Sulfur contents of the main mineralization stage apatite are higher than those of both magmatic apatite and potassic stage apatite, while its Cl content is very low. This implies that copper may have been transported in main hydrothermal stage ore-fomaing fluid in the form of Cu-S complex.
出处
《矿物学报》
CAS
CSCD
北大核心
2007年第1期31-40,共10页
Acta Mineralogica Sinica
基金
国家重点基础研究发展规划项目(G1999043209)
关键词
铜厂斑岩铜矿
磷灰石
岩浆析气
岩浆演化
Tongchang porphyry copper deposit
apatite
magma degassing
magma evolution
metal transport
