摘要
作者按照涂光炽教授的分类将福建省层控铅锌矿床划分为4种类型。本文对它们的地质特征、微量元素和硫、铅同位素组成的特征作了较详细的阐述,对矿床的矿质来源作了初步的探讨。
According to the Tu Guangchi classification, the authors grouped stratabound
lead-zinc deposits in Fujian province into four genetic types, namely: sedimentary
-metamorphic, sedimentary-transformed, sedimentary-late hydatopneumatic su-
perimposed, and epigenetic ore deposits.
The ore-control stratigraphic horizons of sedimentary-metamorphic deposits
are calcic rocks in Daling Formation and Mayuan Formation of Precambrian
blende-galena-pyrrhotite. Sedimentary-transformed and epigenetic deposits have
pyrite chalcopyrite and magnetite beside the association. There occasionally
are, in addition to those minerals, dalarnite and cassiterite in sedimentary-late
hydatopneumatic superityposed deposits.
Composition of trace elements in all the four types of deposits is characterised
by enriching of Ag, Bi and Cd. Ore minerals for four types of deposits differ
in composition of trace elements.
Ag, Bi and Se contents, Bi/Ag and Se/S×10-4 ratios in blende increase with
sedimetary-metamorphic→sedimentary-transformed→epigenetic→sedimentary-late
hydatopneumatic superimposed type. Change of Ag, Bi and Se contents in sedimentary
-metamorphic deposits is smallest among the four types. Chang of Ag, Bi and
Se contents in the three other types is greater than the sedimentary-metamorphic
type by a factor of 2.
Results of R cluster analysis show that grouping of elements for sedimentary
-metamorphic and sedimentary-transformed ores generally accords well with
grouping of elements for ore-bearing strata, but grouping of elements for sedimen-
tary-late hydatopneumatic superimposed ore only partially accords with grouping
of elements for ore-bearing strata.
The origin of sulphur in the four types of deposits are different from each
other. Because of homogenisation sulphur isotopic composition in sedimentary-
metamorphic deposits is stable and equal, and δ34S values are always small
positive numbers. The δ34S values in epigenetic deposits change widely between
larger positive number and smaller negative number. The sulphur in the two above
mentioned types of deposits is of normal sedimentary origin. δ34S values in
sedimentary-transformed and sedimentary-late hydatopneumatic superimposed
deposits are zero, a little larger or smaller than zero. The sulphur might originated
from the deep crust.
Lead isotoopi composition in sedimentary-metamorphic and sedimentary trans-
formed deposits are stable and equal. The lead belongs to the normal common
lead. Lead isotopic model age of the two types of deposits accord well with the
age of ore-perserving strata. The lead is of crustal origin, Lead isotopic composi-
tion in sedimetary-late hydatopneumatic superimposed deposits is characterized by
mixed lead, partly originating from the ore-preserving strata, partly from the
strata under the deposits. Lead isotopic composition in epigenetic deposits is
characterized by U-and Th-rich abnormal lead. The lead belongs to the lead ori-
ginated from the residual crust.
出处
《现代地质》
CAS
CSCD
1990年第1期90-100,共11页
Geoscience
