Mineralization Geochemistry Features Of The Dongping Gold Deposit In Chongli County, Hebei Province

Dongping gold deposit is a new type of gold deposit which is first discovered in alkaline rock mass. It is located in the western part of the Yanshan. The tectonic position of which is in the middle section of the north edge of North China. The host strata of the deposit are the Jiangouhe Formation of Sanggan group in the Archean. It is an amphibolite-granulite faces metamorphic rocks series which composed by a set of hornblende plagioclase gneiss, amphibolite, biotite schist and leptite. The mineralization geological body is Shuiquangou syenite alkaline complex rock, and is distributed in south part of Shangyi- Chongli- Chicheng deep fault zone in the shape of elongated strip. Based on the deposit geological characteristics, the paper systematically analyzes metallogenic structural system, the characteristics of major, trace, rare earth elements and stable isotope, the rock(ore) mineralization age of the Dongping Gold Deposit, to achieve the following main results and understandings:1) Determinated that Dongping gold deposit is a magmatic hydrothermal type middle-high temperature quartz- potassic alteration type gold deposit of Variscan-Yanshan period. There were three types of orebody in the area: auriferous quartz veins and auriferous quartz veinlets type; quartz veins and altered rock vein next to the quartz veins type; potassic-silicified alteration rock type. The relationships among three types of deposits were both interdependent and transitional changes. The auriferous grade decreased by quartz veinsâ†'potassic alteration beltâ†'mineralized wall rock.2) Based on the existing division of the metallogenic stages, pointed that the main gold ore bodies were formed in the quartz polymetallic sulfide stage. The mineralization epoch of Dongping gold deposit could be divided into four stages:â… feldspar-quartz stage; â…¡ quartz- pyrite stage; â…¢ quartz-polymetallic sulfides stage; â…£ pyrite- carbonate stage. The stage â…  had weak gold mineralization, stage â…¡ was significant mineralization stage for gold, stage â…¢ was the main gold mineralization stage and stage â…£ was the final stage, had a little relationship with mineralization3) Identified that the main ore controlling structures were NW and NE strike faults.4) Determined that the mineralizing fluid of Dongping gold deposit was mostly sourced from mantle, few from earth crust. The main elements, trace elements, trace elements, REE, H, O isotopes, Pb isotopes, S isotopes, Rb isotopes, Sr isotopes, and fluid-inclusion composition characteristics and so on, all provide the evidence.5) Two mineralization epochs was ascertained based on the isotopic age data. The early epoch have a certain relationship with the formation of alkaline intrusive complex(393.9 ~ 409.4 Ma), the gold initial enrichment(350.9±0.9 Ma). The later epoch also can be divided into two stages: the main stage is the Early Jurassic period in Yanshanian(175 ~ 200 Ma, altered rock type gold mineralization stage), secondary stage is the Early Cretaceous in Yanshanian(132 ~ 140 Ma, quartz vein type gold mineralization stage).