陕西山阳柞水矿集区燕山期岩体矿物学特征:对岩浆性质及成矿作用的指示
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Characteristic of minerals in the Yanshanian granitic rocks in Shanyang-zhashui ore concentration area: Indicator for the magmatic features and metallogenesis
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    摘要:

    山阳-柞水矿集区位于中秦岭晚古生代弧前盆地中,矿集区内出露有泥盆、石炭系地层,同时发育大量印支期和燕山期的岩浆侵入体。目前的研究显示,矿集区内出露的燕山期岩体在其内部及其与地层的接触带附近发育有强烈的热液蚀变和CuMo矿化。通过对区域内燕山期岩体的矿物学研究表明:岩体发育有大量的钾长石和斜长石,部分已发生蚀变;黑云母是原生的镁质黑云母;角闪石主要属于浅闪石和镁角闪石;绿泥石主要是铁叶绿泥石,同时岩体中还发育有榍石、磷灰石等矿物。根据黑云母和角闪石成分特征可判定山柞地区的燕山期岩体是形成于造山带环境具有壳幔混溶特征的I型花岗岩;各岩体的结晶温度大致相同,在701~789℃之间;岩浆具有较高的氧逸度。根据绿泥石估算出岩体的热液蚀变温度在250~355°C,说明形成蚀变的热液流体属于中高温/中温热液流体。通过对比可以发现:山柞地区燕山期岩体在形成环境、岩浆源区及氧逸度方面与典型的大型、超大型斑岩、斑岩-矽卡岩型CuMoAu矿床的成矿岩体具有相似的特征,而且山柞地区燕山期岩体的黑云母在TiO2、Al2O3和CaO含量及K/Na、Mg/Fe、Mg/(Mg+Fe3++Fe2++Mn)及(Fe3++ Fe2+)/(Mg+Fe3++Fe2+)比值与典型性。但是山柞地区出露的燕山期岩体的黑云母的Ti、Si与AlIV+AlVI、Fe3++Fe2+的特征与典型矿床的成矿岩体中的黑云母成分具有一定的差异;磷灰石中F、Cl和S等挥发份成分,尤其是其中SO3含量明显低于典型矿床成矿岩体,这对于Cu/Mo等成矿元素的富集沉淀具有十分不利的影响;同时山柞地区燕山期岩体普遍形成于较大的深度,也是不利于其形成大规模矿化。总体上,山阳-柞水矿集区内燕山期岩体与典型的斑岩、斑岩-矽卡岩型CuMoAu矿床相比,既有部分有利的成矿条件,也有一些不利条件,虽然难以形成大型矿床,但仍具有形成中小型矿床的潜力,在今后的找矿勘查工作中依然需要重视。

    Abstract:

    Shanyang-zhashui ore concentration area located the Late Paleozoic fore-arc basin of Mid-Qinling Orogenic Belt. There are Devonian and carboniferous strata in the ore concentration area, and a large number of Indosinian and Yanshanian magmatic intrusions exposed in the area. Extensive alteration and CuMo mineralization are occurred on the Yanshanian rocks and the contact between the rocks and strata. Through the research of minerals of the rocks, feldspars in the rocks are potash feldspar and plagioclase, and a part of the feldspars had occurred alteration; biotites are protogenetic magnesia biotite; hornblendes are belong to endenite and magnesia hornblende; chlorites are delessite. Meanwhile, sphene and apatite appear in the Yanshanian rocks. Based on the composition of biotite and hornblende, we deem the rocks exposed in Shangyang-zhashui ore concentration area are I type granite and with the crust-mantle mixed solvent characteristics, which were formed in the orogenic belt environment. The rocks have similar crystallization temperature, which are during 701 °C to 789 °C. Magma of the rocks is with higher oxgen fugacity. On the basis of chlorite, altered temperature of the rocks are estimated, 250~355 °C, in which the Chigou rock had the highest temperature. The altered temperature illustrated the hydrothermal fluids forming the alteration in the rocks are medium-high or medium temperature fluid. Compared the rocks in Shangyang-zhashui ore concentration area with the metallogenic rock bodies of typical large or super-large porphyry deposit and porphyry-skarn CuMoAu deposit, we can find the rocks researched have a lot of similar features with the typical deposit, in forming environment, magmatic source and oxgen fugacity. The contents of TiO2, Al2O3, CaO and the ratioes of K/Na, Mg/Fe, Mg/ (Mg+Fe3++ Fe2++ Mn) and (Fe3++ Fe2+)/ (Mg+Fe3++ Fe2+) are consistent with the typical deposit; the compositions of apatite in the rocks have some similar characteristics with the metallogenic rocks of typical deposit. However, the compositions of Ti, Si and AlIV+AlVI, Fe3++ Fe2+ of biotites in the rocks are different with the metallogenic rocks of typical deposit. And the volatile matters of apatite, as F, Cl and S, are lesser than the typical, especially the content of SO3, which is adverse to ore-forming elements deposit, as Cu or Mo. The rocks were forming a deeper depth, which is a disadvantage for forming large scale mineralization. As a whole, the Yanshanian rocks in Shangyang-zhashui ore concentration have some advantage for forming porphyry or porphyry-skarn deposit, but there are some adverse conditions. Although the rocks are difficult to forming large porphyry or porphyry-skarn deposit, they have the potential to forming small and medium size deposit, so we also need to attach importance to the rocks in ore prospecting work in the future.

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陈雷,闫臻,王宗起,吴发富,王瑞廷,任涛,郭延辉,王鹏.2014.陕西山阳柞水矿集区燕山期岩体矿物学特征:对岩浆性质及成矿作用的指示[J].地质学报,88(1):109-133.
chenlei, yanzhen, wangzongqi, wufafu,王瑞廷,rentao, guoyanhui, wangpeng.2014. Characteristic of minerals in the Yanshanian granitic rocks in Shanyang-zhashui ore concentration area: Indicator for the magmatic features and metallogenesis[J]. Acta Geologica Sinica,88(1):109-133.

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  • 收稿日期:2013-07-19
  • 最后修改日期:2013-08-27
  • 录用日期:2013-09-09
  • 在线发布日期: 2014-01-24
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