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。
There are more than 20 massive sulphide deposits within upper Paleozoic basins in
South China. These deposits occur at the transitional parts from clastic rocks to carbonates adja-
cent to the bottom of the marine transgression sequences, and are accompanied with minor bi-
modal 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 stratigra-
phycally vertical and lateral zonations, which were produced by a combination of exhalation-diage-
nesis, 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
formed under more oxidizing environments, exhalative iron-manganese ore layers are often under-
lain by vein-type lead-zinc and gold mineralizations. Such a type of upper Palaeozoic disconcordant
hydrothermal mineralizations in basement sequences should be paid great attention to during min-
eral 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 Palaeo-
zoic 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 mag-
matic 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.
出处
《高校地质学报》
CAS
CSCD
2003年第4期592-608,共17页
Geological Journal of China Universities
基金
国家自然科学基金(50234051)
关键词
块状硫化物矿床
大陆地壳
海底喷流
断裂拗陷
同生断裂
长江中、下游
华南
massive sulphide deposit
continental crust
submarine exhalation
fault depression
growth fault
lower Yangtze
South China
