黔南泥盆系重晶石矿床地质特征与成矿规律

Geological characteristics and metallogenic regularities of the Devonian barite deposits in the southern part of Guizhou Province

对黔南泥盆系重晶石矿床的产出地质背景、矿床地质和同位素地球化学特征进行了综合分析,总结了重晶石矿床空间分布特征和成矿规律,指出了可能的成矿远景区。重晶石矿床空间展布形态及产出特征受北西向区域性深大断裂控制明显,矿体呈北西向沿褶皱或次级断裂分布。矿石结构、构造类型在乐纪矿段最为多样,包括纹层状、条带状、块状、碎屑状和角砾状构造,且矿体厚度最大,约10 m;向东部罗城矿段过渡,矿石构造类型主要以纹层状和块状构造为主,矿体厚度迅速减薄或尖灭。矿石S同位素组成从乐纪至罗城,δ^(34)S值由+68.4‰迅速降低至+27.6‰,指示乐纪地区相比罗城一带,可能处于更深水的局限环境,硫酸盐还原细菌作用更加强烈。重晶石矿体中与古甲烷渗漏事件有关的球状灰岩,其δ^(13)C值在乐纪矿段表现最负,为–10.27‰,罗城矿段灰岩δ^(13)C值逐渐偏正,达到+0.03‰,说明古甲烷渗漏活动在乐纪矿段表现更剧烈,强烈的渗漏事件为形成厚度约10 m的重晶石矿体提供了充足的物质保障。镇宁乐纪地区很可能是重晶石成矿的中心,向东部罗城一带过渡,逐渐远离成矿中心,成矿物质供应匮乏,不易形成具有经济价值的工业重晶石矿体。此外,应重视并加强乐纪以西地区重晶石找矿勘查工作,重点是寻找北西向断裂或褶皱构造发育地区,重晶石成矿条件相比更加优越,易在隐伏重晶石矿床找矿方面取得新突破。

This paper analyzed the geological setting and geochemical characteristics of the Devonian baritedeposits in the southern part of Guizhou Province.The authors summarized the spatial distribution features andmetallogenic regularities of barite deposits,and delineated the metallogenic prospect areas.The barite ore bodiesare distributed along the NW-trending folds or secondary faults,and their distribution and occurrence arecontrolled by regional deep faults.In the Leji section,barite structure and tectonic type vary most seriously,including laminar,banded,massive,fragmental and brecciated structures.Moreover,their thickness reaches themaximum,up to10m.From the Leji section to the Luocheng section,the barite ore bodies gradually decreases inthickness and their structural types also become less.Theδ34S values of barite gradually decrease from+68.4‰inLeji to+27.6‰in Luocheng,which implies that the depositional environment in the Leji area is a deeper waterarea of the restricted rift basin compared with other areas.The spherical carbonates are associated with methane seeps in the barite deposits,and theirδ13C values increase from–10.27‰in Xiyahe to+0.03‰in Luocheng,which indicates the gradually weakening strength of the methane seep activities.Compared with other sections,the stronger leakage event of methane would lead to the formation of a10m barite ore body in Leji.Incombination with all the previous and present data,we suggest that the ore-forming center of barite deposits maybe located in the Leji area or close to the Leji area.As a result,the potential prospecting areas would be locatedaround the Leji area.In addition,it is suggested that future prospecting for barite deposits in the Leji area must beconcentrated on the areas where NW-trending faults and folds are well developed,which might lead to abreakthrough in finding more concealed barite deposits.