甘肃狼娃山铁矿床火山岩地球化学特征及其对铁成矿的制约

狼娃山铁矿床位于中亚造山带西南缘的北山多金属成矿带中，为甘蒙北山地区主要的铁矿床之一。为探寻狼娃山铁矿床中火山岩对铁成矿的影响，本文通过系统的野外地质调查、全岩及单矿物主微量元素分析等方法，阐明了狼娃山矿床下石炭统火山岩的构造背景、成矿物质来源及火山活动对铁成矿的影响。研究结果表明，该矿床火山岩形成于晚古生代活动大陆边缘局部伸展作用环境；矿床下石炭统白山组火山岩与火山口相火山岩具有极为相似的岩相学特征，铁矿的产出受控于喷发—喷溢相岩层；火山岩具有高的SiO₂、Na₂O、K₂O、CaO/(Na₂O+K₂O)、A/CNK(0.85～1.89)值和低的P₂O₅、TiO₂含量，指示了矿体形成主要与喷发过程的岩浆分异作用有关。综合研究认为，狼娃山铁矿床的形成与下石炭统白山组中酸性火山岩具有密切成因联系，未来找矿方向应主要关注于熔结凝灰岩及部分凝灰岩岩层。

Geochemical characteristics of volcanic rocks and their constraints on Fe mineralization in the Langwashan Fe deposit， Gansu Province

The Langwashan Fe deposit is located in the Beishan polymetallic metallogenic belt of the southwestern Central Asia Orogen. It is one of the main Fe deposits in the Beishan area of Gansu and Inner Mongolia. In order to explore the influence of volcanic rocks on Fe mineralization in the Langwashan Fe deposit， in this paper， through systematic field geological survey， whole rock and single mineral major and trace element analysis， the metallogenic tectonic background， ore-forming material source， and volcanic activity of the Lower Carboniferous volcanic rocks in the Langwashan deposit are clarified，and the influence of magmatism on Fe mineralization is also constrained. The results show that the volcanic rock of this deposit was mainly formed in the local extensional environment of an active continental margin in late Paleozoic. The volcanic rocks of Lower Carboniferous Baishan formation and volcanic rocks of volcanic crater facies have very similar petrographic characteristics， and the occurrence of Fe ore was controlled by eruptive effusive facies rocks. Volcanic rocks have high SiO₂， Na₂O， K₂O， CaO/（Na₂O+K₂O）， A/CNK （0.85-1.89）， whereas low P₂O₅ and TiO₂ contents， indicating that the formation of ore bodies was mainly related to the differentiation of magmatic eruption process. The comprehensive study shows that the formation of the Langwashan Fe deposit was closely related to Lower Carboniferous Baishan intermediate-acidic volcanic rocks， and the future prospecting direction should mainly focus on ignimbrite and some tuff rocks.