青海省群力铁矿成矿特征及找矿潜力分析

Mineralization Characteristics and Prospecting Potential of the Qunli Iron Deposit in Qinghai Province

青海群力铁矿床大地构造位置隶属于东昆仑造山带祁漫塔格-都兰造山亚带中西段的祁漫塔格结合带的祁漫塔格-都兰华力西期铁、钴、铋、铅、锌、铜、银成矿带野马泉矿集区内,是青海省著名的铁多金属矿成矿富集区之一。前人对该区基础地质和成矿特征等方面进行了大量的研究,并提出该区成矿类型主要为矽卡岩型、热液型,其次为斑岩型,成矿与晚古生代-早中生代中酸性侵入体关系密切,但一些铁矿的成因尚不明确。笔者通过对群力铁矿矿床地质特征、混合岩化特征、矽卡岩特征、矿体赋存特征、矿床成矿类型和成因进行综合分析,认为群力铁矿不是中酸性侵入岩与碳酸盐岩接触交代成矿,而是赋存于古元古代金水口岩群混合岩化片麻岩夹大理岩系透辉石透闪石矽卡岩中,是片麻岩在混合岩化作用叠加热液交代作用下形成的层状矽卡岩成矿,其矿体规模与层状含矿矽卡岩规模呈正相关,与围岩界线较明显,具有远离岩体矿化富集、靠近岩体贫化的特征,形成的矿体多为盲矿体,向西侧伏特征明显,向更深部仍有含矿矽卡岩分布,深部找矿潜力较大。

In tectonics,the Qunli iron ore deposit of Qinghai lies in the the East Kunlun orogenic belt.It is part of the Yemaquan ore concentration area of the iron,cobalt,bismuth,lead,zinc,copper and silver metallogenic belt of the Qimantage-Dulan Variscan period,one of the famous iron polymetallic mineralization areas in Qinghai Province.There are a lot of previous studies on the basic geology and metallogenic characteristics of this area,suggesting that its mineralization is dominated by skarn and hydrothermal types,followed by porphyry,closely related to the intermediate acid intrusive bodies of Late Paleozoic-Early Mesozoic,while the genesis of some iron ores remains unclear.To address this issue,this work made a comprehensive analysis of the geological characteristics,migmatization features,skarn,ore body occurrence,metallogenic types and genesis of this iron deposit.Results suggest that the Qunli iron ore is not metasomatic mineralization between intermediate acid intrusive rock and carbonate rock,instead hosted by a diopside tremolite skarn of the Paleoproterozoic Jinshuikou Group mixed with migmatized gneiss and marbles.Its iron ore is a kind of layered skarn mineralization formed by gneiss under the action of migmatization and hydrothermal metasomatism.The size of the ore body is positively correlated with the size of the layered ore-bearing skarn,and the boundary between the ore body and the surrounding rock is obvious.It is characterized by a large distance to the mineralization and enrichment of the rock body,and proximity to the depletion of the rock body.Most of the ore bodies are blind ones,with obvious westward dipping characteristics.Ore-bearing skarns may extend downward to the deep subsurface,implying a large prospecting potential.