DOC《西藏仁布念扎金矿矿床成因及找矿标志》

西藏仁布念扎金矿矿床成因及找矿标志 冯志红,余璨(中国有色金属工业昆明勘察设计研究院,云南 昆明 650051) 摘要:念扎金矿位于冈底斯铜(钼)成矿带南部,产于强片理化及褪色蚀变超基性岩片与燕山期石英闪长岩体的接触边部.

矿体主要赋存于含矿构造带蚀变破碎带,多呈脉状产出,厚度较稳定且矿化较均匀,矿区内地质构造复杂,矿体空间展布及富化主要受控于NW向断裂,NE向断裂则主要为破矿构造,矿区内褐铁矿化、硅化、碳酸盐化与矿化呈正相关.本文通过对矿床成矿背景及成矿规律的总结,表明矿化主要受地层岩性(围岩)、构造及围岩蚀变控制,属于构造蚀变型金矿床,并提出各含矿带深部、倾向延伸部分及石英脉集中地段找矿潜力较大,可为相似成矿条件矿段的地质勘查工作提供理论指导. 关键词:金矿;

矿床成因;

找矿标志;

找矿前景;

西藏仁布 中图分类号:TD15,P618.51 文献标识码:A 文章编号: Ore genesis and prospecting criteria of Nianzha gold deposit in Renbu County, Tibet Province FENG Zhi-hong,YU Can (Kunming Institute of Exploration &

Design, China Nonferrous Industry Company Ltd , Kunming 650051, Yunnan) Abstract: Nianzha gold deposit is located in the southern Gangdise metallogenic belt, which outputted in the contact edge between strong schisteous-fade alteration ultramafic schist and Ynshanian quartz diorite rock mass. The gold ore-body is hosted by altered fracture zone of ore-bearing structure, which occurs as vein-like. Besides, the ore-body characterized by relatively stable thickness and uniform mineralization. The Nianzha gold mining area is characterized by complex tectonic framework which the NW-trending fracture as the main ore-bearing structure, has the close relationship with mineralization, and the NE-trending structure is the ore-breaking structure. The limonitization, silicification, carbonation has positive correlation with mineralizaiton. According to the systematic summary of the geological background, strata, tectonic, rock mass and alteration characteristics, this paper concluded that the Nianzha gold deposit is a structurally-controlled-altered type gold deposit, which main controlled by formation lithology (surrounding rock), tectonic and rock alteration. In addition, this research showed that the deep part of ore-bearing belt, extending part along the tendency and the quartz-vein concentrated section have the better prospecting potential, which could be the prospecting guideline in other area with the similar geological setting within the Nianzha mining area. Key words: gold deposit;

ore genesis;

prospecting criteria;

prospecting potential;

Renbu County in Tibet 0引言 念扎金矿区总体位于冈底斯成矿带上,区内经历了多期次不同尺度、不同成因的构造运动,形成了以雅鲁藏布江北界断裂(F4)为界彼此共生的复杂构造格局,叠加区内频繁的岩浆活动,为区域提供了有利的成矿条件[1-6].目前,本区所属的冈底斯铜(钼)成矿带[7]上已相继发现冲江[8-10]、白荣[11]、驱龙[12-15]及甲玛[16-18]等斑岩型铜多金属矿床及克鲁、冲木达等矽卡岩型铜金矿,均具大型、超大型矿床远景[19-21].念扎金矿作为区域南部的代表性矿床,尽管成矿背景良好但总体工作程度较低,文章在对矿床地质特征进行分析的基础上,总结控矿因素及矿床成因,厘定矿床有利的找矿标志,并提出矿区有利的找矿部位,为下一步地质勘查工作提供依据. 1成矿地质背景 区域大地构造总体呈 两片(区)夹一带 (图1),以区域中央雅鲁藏布江结合带为界,南部为喜马拉雅块北缘,北部则为冈底斯-念青唐古拉板块南缘.区内主要出露三叠系、白垩系及古近系地层,以三叠系宋热组最为发育,该地层同时受近EW向两条蛇绿构造混杂岩带的韧性剪切作用.此外,受频繁岩浆活动及构造运动的影响,区内侵入岩发育,尤以超基性岩体分布最为广泛,其北部的侵入岩为矿床的形成提供了主要矿源及热驱动力,与矿产关系密切.区域南部基性-超基性构造推覆岩片指示着特殊的构造痕迹,念扎金矿既是产于强片理化及褪色蚀变超基性岩片与北部燕山期石英闪长岩体的接触边部,可见不同程度的金矿化蚀变. 图1 念扎金矿大地构造位置图 Fig.