北山青白口纪红山铁矿床成因  

Genesis of the Qingbakou Period Hongshan Iron Ore Deposit in the Beishan Area,Gansu Province

作　　者：王兴保 WANG Xing-bao(Northwest Geological Exploration Institute of China General Administration of Metallurgical Geology,Xi'an,Shaanxi 710119)

机构地区：[1]中国冶金地质总局西北地质勘查院,陕西西安710119

出　　处：《地质与勘探》2018年第S01期1402-1408,共7页Geology and Exploration

摘　　要：北山青白口纪晚期含铁层系的沉积海盆长度大于200km,宽大于50km。已经发现多处大型沉积变质磁铁矿床。其中,红山铁矿床,已提交铁矿石储量1.6亿吨;天湖铁矿床,铁矿石储量1.3亿吨;杨岭铁矿床,铁矿石远景资源量1亿吨左右。北山青白口系上部皆有中基性到中性火山岩,并都有与火山活动成因相关的沉积变质铁矿存在,这反映了青白口纪是既有稳定的以碳酸盐沉积为主的滨浅环境又有半活动到活动的碎屑岩夹火山岩的半深海环境。(1)红山铁矿床铁矿石中含有大量灰紫色碧玉团块和硅质条带,通过硅质岩的地球化学特征研究发现,该矿区硅质岩为海底热水沉积物,代表了呈凝胶体沉积在海底上的热液喷发的二氧化硅相和铁。(2)通过研究围岩蚀变类型发现其是在含铁高温热卤水在喷流通道涌出时,把成矿前的矿层底板沉积岩系进行岩水反应。本矿区的围岩蚀变作用是一种海底变质作用。(3)红山铁矿床沉积环境由北东到南西依次为滨浅海沉积环境、浅海深水环境以及半深海海底喷发环境。(4)研究认为红山铁矿为与火山活动有关的沉积变质型铁矿床。The sedimentary basin of iron-bearing strata of the late Qingbakou period in the Beishan area is more than 200 km long and over 50 km wide.A number of large-scale sedimentary metamorphic magnetite deposits have been found there,of which the Hongshan iron ore deposit has submitted 160 million tons of iron ore and the Tianhu iron deposit hosts130 million tons iron ore reserves,and the Yangling iron ore deposit has prospective resources of iron ore about 100 million tons.In the upper part of the Qingbaikou system in Beishan,there are intermediate to neutral volcanic rocks as well as sedimentary metamorphic iron ores related to the genesis of volcanic activity.This reflects that the Qingbakou period was a semi-deep-sea environment in which there were both stable shore-shallow environments dominated by carbonate deposits and semi-active clastic rocks intercalated with volcanic rocks.(1)The iron ore of Hongshan iron ore deposit contains a large number of grayish-purple Jasper agglomerates and siliceous belts.Geochemical characteristics of siliceous rocks suggest that the siliceous rocks in this area are submarine hydrothermal sediments.It represents the silica facies and iron from hydrothermal eruptions deposited on the bottom of the sea by gel bodies.(2)Study on the alteration types of surrounding rocks reveals that when the hot brine containing iron was gushing out in the jet flow channel,the sedimentary rock series on the floor of ore-bed before mineralization was reacted with rock and water.The alteration of surrounding rocks was a kind of submarine metamorphism.(3)The sedimentary environments of the Hongshan iron deposit from north east to south west were offshore,shallow sea with deepwater,and semi-deep sea with seafloor eruption.(4)The Hongshan iron deposit is considered to be a sedimentary metamorphic iron deposit related to volcanic activity.

关 键 词：北山红山铁矿 青白口纪 火山活动 沉积变质 

分 类 号：P618.31[天文地球—矿床学]