湘西花垣铅锌矿田成矿构造系统与成矿规律

The metallogenic structural system and metallogenic regularity of the Huayuan lead-zinc orefield in western Hunan Province

湘西花垣铅锌矿田发育典型的层控型铅锌矿床,找矿潜力巨大。该区在矿床成因、控矿因素等方面存在不同认识,主要观点有密西西比河谷型、沉积型、成岩期后改造型和盆源低温热液型4种观点。通过构造测量解析和古应力场恢复,分析了构造与成矿的关系,划分出成矿前构造主压应力近似垂直层面,成矿期构造主压应力方向为北西—北北西,成矿后构造主压应力方向为北东—北北东向;成矿期构造形成了矿田内李梅平缓背斜、渔塘背斜,并在藻灰岩层内形成各类含矿角砾岩、裂隙系统,这些裂隙为热液与藻灰岩中富含的有机质发生化学反应提供了丰富的反应界面,是铅锌矿液富集的主要原因。成矿后构造主要形成于燕山期,受北北东—南南西向挤压应力作用,形成了北东走向的大型走滑正断裂带,对加里东期成矿期赋矿褶皱造成破坏改造。

Typical stratabound lead-zinc deposits are developed in the Huayuan lead-zinc orefield,western Hunan Province,with great prospecting potential.Many researchers have systematically studied the geological characteristics of the deposits in this area,but there are different opinions on the genesis of the deposits and ore-controlling factors.There are four main viewpoints:Mississippi Valley type,sedimentary type,post-diagenetic reformation type and basin-source low-temperature hydrothermal type.In this paper,the relationship between structure and mineralization was analyzed by means of structural measurement and analysis and palaeostress field recovery,and the tectonic stress was divided into three stages:the principal compressive stress of premetallogenetic structure is in approximately vertical direction to layers,and the principal compressive stress of metallogenic period is in NW-NNW direction,the principal compressive stress after mineralization is in NE-NNE direction.The Limei gentle anticline and Yutang anticline were formed in the orefield during the metallogenic period,and various ore-bearing breccias and fracture systems were formed in the algal limestone layer.These fractures provided a rich reaction interface for the chemical reaction between the hydrothermal solution and the organic matter in algal limestone,which seems to be the main reason for the enrichment of the lead-zinc ore solution.Post-metallogenetic structure was formed during Yanshanian period.A large strike-slip normal fault zone was formed under NNE-SSW compressional stress,which destroyed and reworked the ore-bearing fold during the Caledonian period.