Geology, alteration, age, and origin of iron oxide–apatite deposits in Upper Eocene quartz monzonite, Zanjan district, NW Iranстатья
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Дата последнего поиска статьи во внешних источниках: 27 марта 2014 г.
Аннотация:Iron oxide–apatite deposits are present in Upper
Eocene pyroxene-quartz monzonitic rocks of the Zanjan district,
northwestern Iran.Mineralization occurred in five stages:
(1) deposition of disseminated magnetite and apatite in the
host rock; (2) mineralization of massive and banded magnetite
ores in veins and stockwork associated with minor brecciation
and calcic alteration of host rocks; (3) deposition of sulfide
ores together with potassic alteration; (4) formation of quartz
and carbonate veins and sericite, chlorite, epidote, silica, carbonate,
and tourmaline alteration; and (5) supergene alteration
and weathering. U–Pb dating of monazite inclusions in the
apatite indicates an age of 39.99±0.24 Ma, which is nearly
coeval with the time of emplacement of the host quartz monzonite,
supporting the genetic connection. Fluid inclusions in
the apatite have homogenization temperatures of about 300 °C
and oxygen isotopic compositions of the magnetite support
precipitation from magmatic fluids. Late-stage quartz resulted
from the introduction of a cooler, less saline, and isotopically
depleted fluid. The iron oxide–apatite deposits in the Tarom
area of the Zanjan district are typical of a magmatic–hydrothermal
origin and are similar to the Kiruna-type deposits with
respect tomineral assemblages, fabric and structure of the iron
ores, occurrence of the ore bodies, and wall rock alteration.