甘肃公婆泉浅海相含铜斑岩的地质与地球化学特征

来源期刊：中国有色金属学报1998年第3期

论文作者：雷良奇 宋慈安 杨启军

文章页码：523 - 528

关键词：斑岩铜矿； 斑岩； 甘肃公婆泉

Key words：porphyry copper ； porphyry； Gongpoquan； Gangsu

摘    要：与大多数含铜斑岩产于陆相火山岩区不同，甘肃公婆泉含铜斑岩(即英安斑岩和花岗闪长斑岩)在空间和成因上与中-晚志留世浅海相火山岩系关系密切。这两类含铜斑岩均侵入于石英粗面岩中，斑晶矿物成分、 斜长石牌号、 岩石化学成分、铁族及成矿元素的丰度等相近， 均属钙碱性岩系(里特曼指数为1.69～2.75)， 具富K(K₂O为2.80%～4.77%)、 低A l(Al₂O₃为14.46%～16.01%)、 低Ca(CaO为2.49%～4.63%)及成矿元素含量较高的特点。 与花岗闪长斑岩相比较， 英安斑岩的斑晶含量较低而晶屑含量较高、 钾化蚀变较强烈、 Fe₂O₃ /FeO值和K₂O含量较高、CaO含量较低。 两类斑岩是同源岩浆的浅成-超浅成侵入体， 英安斑岩的侵位深度相对较浅。

Abstract: In the world, most of the bearing-copper porphyries occur at the zone of the continental volcanic rocks, but the situation is very different in the Gongpoquan copper ore field: the porphyries(dacite porphyry and granodiorite porphyry)occur at the area of the marine volcanic rocks. These two sorts of porphyries invaded into the S_2-3 quartz trachyte, and they are similar in the mineral composition of porphyritic crystal, number of feldspar, chemical composition of rock, and element abundance(V, Cr, Mn, Co, Ni, Zn, Mo, Sn, W, As, etc). In addition, the por phyries belong to the lime-alkali series(δ=1.69~2.75) and are characterized by higher K₂O(2.80%~4.77%), lower Al₂O₃(14.46%~16.01%), lower CaO(2. 49%~4.63%), and higher minerogenetic element abundance. On the other hand, comparing with the granodiorite porphyry, the dacite porphyry holds the following different charaters: less quantity of porphyritic crystal and more quantity of crystalloclastic, more intensive K-alternation, higher Fe₂O₃/FeO and K₂O, and lower CaO. Accordingly, these porphyries are shallow invasive body from the same magma chamber, and the invasive depth of the dacite porphyry is more shallow than the invasive depth of the granodiorite.