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再论大陆地壳断裂拗陷带中的华南型块状硫化物矿床

顾连兴1, 胡文瑄1, 倪培1, 何金祥2, 徐跃通3, 陆建军1, 林春明1, 李伟强1   

  1. 1. 南京大学内生金属矿床成矿机制研究国家重点实验室,地球科学系,南京 210093; 2. 中国地质矿产信息研究院,北京 100037 ; 3. 山东师范大学地理系,济南 250014
  • 收稿日期:2003-12-20 修回日期:2003-12-20 出版日期:2003-12-20 发布日期:2003-12-20

New Discussion on the South China-Type Massive Sulphide Deposits Formed on Continental Crust

GU Lian-xing1, HU Wen-xuan1, NI Pei1,HE Jing-xiang2, XU Yue-tong3, LU Jian-jun1, LIN Chun-ming1, LI Wei-qian1   

  1. 1. State Key Laboratory of Mineral Deposits Research ( Nanjing University), Department of Earch Sciences, Nanjing University, Nanjing 210093, China; 2. Chinese Institute of Geology and Mineral Resources Information, Beijing 100037, China; 3. Department of Geography, Shandong Normal University, Jinan 250014, China
  • Received:2003-12-20 Revised:2003-12-20 Online:2003-12-20 Published:2003-12-20

摘要: 华南海西-印支断裂拗陷带中的块状硫化物矿床(MSD)主要产于晚古生代海侵岩系底部附近碎屑岩向碳酸盐地层的过渡部位,含矿岩系中伴有少量双峰式火山岩和大量喷流岩,矿床中最基本的矿物共生关系是变质反应关系,金属元素和矿物相的分布往往显示地层学垂直分带和侧向分带,这种分带是同生沉积-成岩、活化转移和后期改造叠加等因素综合作用的产物。层状矿体下盘可以存在着代表海底热液通道的脉状、角砾状和浸染状矿化,与之伴生的硅化、绢云母化和钾长石化等蚀变反映了大陆地壳及其沉积物的富硅、富钾特征。与块状硫化物呈相变关系的层状铁锰矿床下方可存在脉状铅锌和金矿床。南岭地区的断裂拗陷带形成于后加里东大陆内部,而长江中下游则处于向被动陆缘演化的环境。两个地区晚古生代MSD在成分和成矿特征等方面的一系列差异,反映了成矿时基底陆壳成熟度的差异,而钨和锡则是成熟陆壳上MSD的特征元素。与国外苏利文型明显不同的是,华南地区矿床除了与确定无疑的火山岩伴生外,所含有用金属更加丰富多彩,并且往往受到后期花岗岩类岩浆及其热液的改造和叠加,因此可称之为华南型矿床。并以此代表大陆地壳上MSD的成矿特征。

Abstract: There are more than 20 massive sulphide deposits within upper Paleozoic basins in South China.These deposits occur at the transitional parts from elastic rocks to carbonates adjacent to the bottom of the marine transgression sequences,and are accompanied with minor bimodal volcanites and voluminous exhalites in the host strata.Principal mineral parageneses in the ores are formed by metamorphic reactions.Metals and mineral phases commonly exhibit stratigraphycally vertical and lateral zonations,which were produced by a combination of exhalation-diagenesis,post-ore remobilization,reworking and overprinting.Footwall mineralisations in the form of veins ,breccias and disseminations under massive sulphide layers have been found representing sub-seafloor pathways of ore-forming fluids. Accompaying alterations featured by silicification, sericitization and K-feldspathization can be interpreted to represent the silicon and potassium-rich characteristics of the continental crust.As stratigraphical equivalents to massive sulphides but form ed under more oxidizing environments,exhalative iron-manganese ore layers are often underlain by vein-type lead-zinc an d gold mineralizations.Such a type of upper Palaeozoic disconcordant hyarothermal mineralizations in basement sequences should be paid great attention to during mineral prospecting in South China. Ore-forming basins in the Nanling region were initiated on a post-Caledonian highly-matured contiental crust,whereas the lower Yangtze basin was situated on a basement evolving towards a passive continental margin.Contrasting compositional and metallogenic features of upper Palaeozoic massive sulphide deposits indicate difference in crustal maturity between these two regions during ore formation.Tungsten and tin are characteristic elements of massive sulphides formed on matured continental crust.Deposits in South China are distinct from those of the Sullivan-type in their close association with well-defined volcanic rocks,in their more abundant industrial metal varieties ,and in their strong reworking and overprinting by late-stage granitic magmas and magmatic fluids,and thus are worthy to accept the term South China-type deposits and to be regarded as representative of massive sulphide deposits formed on intensely attenuated continental crust.