印度尼西亚苏拉威西岛北部Buol县砂金矿地质特征及成因浅析

Geologicalcharacteristics and genesis of the placer gold mineral deposits in Buol County, northern Sulawesi, Indonesia

苏拉威西岛位于印度尼西亚群岛的中心,在其北部分布大量砂金矿。通过对Boul县砂金源区的矿体规模、矿化特征、成矿类型和剥蚀淋滤程度调查,结合河谷砂金现场淘洗和试生产情况,认为砂金主要富集于河流中游地区,其次为上游地区,具体可归结为富集于河流拐弯处凸岸的“胃口袋”阶地、河流由窄变宽或两条河流汇合呈“Y”型的外侧以及河床坡度由陡变缓地区。该区砂金矿具有“金源丰富”,“成矿时代新”、“离矿源近”、“成矿过程短”的特点。按砂金矿产出位置认为砂金矿成因类型主要是冲积型,其次为洪积型和残坡积型。原生金矿可能是该地区砂金的主要物质来源,原生金矿先后经历风化带中金的次生加大和富集过程(化学成因)→机械搬运和沉积分异作用(机械成因)→形成砂金矿。此认识可为该地区寻找砂金提供一定借鉴意义。

Sulawesi island is located in the center of the Indonesian archipelago,a large number of placer gold deposits are distributed in the north of Sulawesi island.The author investigated the scale of ore body,mineralization characteristics,mineralization type and denudation leaching degree of placer gold source area in Boul County.Comprehensive analyze the conditions of gold washing and pilot production in the valley,it is believed that gold placer is mainly concentrated in the middle reaches of the river,secondly,it’s enrich in the upper reaches of the river.For example,the shape of the ares like“stomach pockets”at the convex banks of rivers;The place of the river changes from narrow to wide;The area where the two rivers converge on the outside is like a“Y”shaped river,and the slope of the river bed changes from steep to slow.The gold place minerals have the characteristics of the“rich gold source”,“new metallogenic era”,“near the mine source”and“short metallogenic process time”.According to the location of placer gold deposits,it is considered that placer gold deposits of alluvial type is the mainly the genetic types in the study area,closely followed by proluvial type and eluvial slope type of the placer gold.The main material source of placer gold may be from the primary gold deposits.Primary gold deposit experience secondary enlargement and enrichment of the gold in weathering zone,which belongs to chemical origin in placer gold deposits.Then,going through the mechanical transport and sedimentary differentiation.Finally,it is formed placer gold deposits.