黑龙江多宝山-呼玛地区金矿分类及成矿地质背景研究

RESEARCH ON THE CLASSIFICATION AND METALLOGENIC BACKGROUND OF GOLD DEPOSITS IN DUOBAOSHAN-HUMA AREA, HEILONGJIANG PROVINCE

黑龙江省西北部的多宝山-呼玛地区发育大小型金矿(点)16处,主要集中分布在北东向和北西向构造形成的菱环形构造带内.元古宇和下古生界地层单元为金成矿提供物质来源,古生代以来3阶段强烈岩浆热事件为金矿成矿提供了热源、流体和就位空间.根据金矿床赋矿岩石类型、成矿流体等特征和区域构造演化过程,将本地区金矿划分为3个类型:1与火山岩有关的浅成低温热液型金矿,赋矿围岩为早白垩世火山岩,成矿流体源于大气降水;2受压扭性构造控制的低温热液金矿,对围岩无选择,成矿流体具有变质流体和大气降水混合特征,低盐度,少CO2;3夕卡岩型、斑岩型伴生金矿床,具有成矿温度高、盐度高、流体包裹体富含CO2的特点.第一类与第二类为同期异相,形成环境为造山后陆内裂谷-伸展环境;第三类形成于与古太平洋板块的斜向俯冲作用和北部鄂霍次克洋闭合有关的挤压造山环境.

Dozens of gold deposits have been discovered in Duobaoshan-Huma area in the northwestern part of Heilongjiang Province,which are distributed mainly in a rhombic area composed of NE-trending and NW-trending structures.The Proterozoic and Lower Paleozoic stratigraphic units may be the provenance of gold.Three stages of tectonomagmatic thermal events since Paleozoic have provided the heat,fluid and space for metallogenesis.Based on the characteristics of host rocks,ore-forming fluids and regional tectonic evolution of the deposits,it is suggested that the gold deposits in this area divide into three genetic types,i.e.1） volcanic rock-related epithermal type,hosted by Early Cretaceous volcanic rock,with ore-forming fluid from meteoric water; 2） epithermal type gold deposits controlled by compressional structure,without choice for host rock,with mixed ore-forming fluid from meteoric water and metamorphic fluid,low salinity and less CO2; and 3） skarn-type and porphyry-type of associated gold deposits,with high mineralization temperature,high salinity and CO2-rich fluid inclusions.The former two types were formed in the same period but located in different tectonic level,in the geological environment of post orogenic extension.The third type of gold deposits were formed in compressive orogenic environment related to the subduction of paleo-Pacific plate and the closure of Mongol-Okhotsk ocean in Late Triassic-Middle Jurassic period.