熊耳山—外方山矿集区中生代Au-Mo成矿系统

Mesozoic Au-Mo metallogenic system in the Xiong’ershan-Waifangshan ore field

熊耳山-外方山矿集区位于秦岭造山带之华北板块南缘,经历了复杂的碰撞造山过程,成矿时间跨度大,成矿强度高,成矿作用多样。复合造山过程和相应的成矿作用已被深入研究,但成矿系统的划分和叠加成矿作用尚需研究。本文将熊耳山-外方山矿集区发育的Au-Mo矿床划分为造山型Mo矿床、斑岩型Mo矿床、岩浆热液脉型Mo矿床、造山型Au矿床和岩浆热液型Au矿床5个类型,对应5种成矿系统:(1)造山型Mo矿床形成于250~227Ma的同碰撞环境和227~194 Ma的后碰撞环境,为变质热液萃取壳源Mo成矿;(2)斑岩型Mo矿床形成于163~135Ma的洋陆俯冲环境和135~116 Ma的岩石圈减薄环境,为岩浆热液携带幔源或壳源Mo成矿;(3)岩浆热液脉型Mo矿床形成于227~194Ma的后碰撞环境,为岩浆热液携带幔源Mo成矿;(4)造山型Au矿床在三叠纪发生了预富集作用,主要形成于163~135Ma的洋陆俯冲环境和135~103Ma的岩石圈减薄环境,为变质热液萃取壳源Au成矿;(5)岩浆热液型Au矿床仅形成于135~103 Ma的岩石圈减薄环境,为岩浆热液携带壳源Au成矿。矿集区主要存在两种叠加成矿作用,即不同构造背景下多种成矿系统的叠加和同一构造背景下不同成矿系统的叠加。

The area of the Xiong’ershan-Waifangshan ore field at the southern margin of the North China Craton,Qinling Orogen experienced complex orogenic processes,resulting in prolonged metallogenic intervals during which extensive metal deposits with diverse mineralization types are formed.Although these complex orogenic processes and related mineralization have been studied extensively,the metallogenic system division and superimposed mineralization are still to be addressed.In this paper,we divide Au and Mo deposits of the Xiong’ershan-Waifangshan ore field into five types,including orogenic,porphyry and magmatic hydrothermal vein molybdenum ore deposit types,and orogenic and magmatic hydrothermal gold ore deposit types.The five types of ore deposits correspond to five kinds of metallogenic systems:(1)Orogenic Mo deposits formed in syn-and post-collision backgrounds during 250-227 and 227-194 Ma,respectively,from ore forming fluids composed of metamorphic water and crustal Mo;(2)Porphyry Mo deposits formed in subduction and crustal thinning environments during 163-135 and 135-116 Ma,respectively,from magmatic fluids carrying crustal or mantle Mo;(3)Magmatic hydrothermal vein type Mo deposits only formed in post-collision tectonic setting during 227-194 Ma from mantle fluid and Mo;(4)Orogenic gold deposits,after pre-mineralization in the Triassic,formed mainly in subduction environment during 163-135 Ma and crustal thinning background during 135-103 Ma,from metamorphic water extracted crustal Au;and(5)Magmatic hydrothermal gold deposits only formed in crustal thinning background during 135-103 Ma from crustal gold.We also found two kinds of superimposed mineralization:superposition of different mineralizations under either different or same tectonic settings.