Genesis Of The Huoshenmiao Mo Deposit, Luanchuan County, Henan Province

The Huoshenmiao Mo deposit is a skarn deposit in the west of the Luanchuan ore concentration area. In order to identify the genesis of the deposit, based on the study of geological characteristics of the deposit, electronic probe, geochronology, lithogeochemistry, fluid inclusions and stable isotopes were used to study the genesis of the Huoshenmiao pluton, formation age of the deposit, nature and evolution of the ore-forming fluids and source of the ore-forming materials, discuss the genesis of the deposit, and the main results and understandings are as follows:1. The orebodies mainly occur in calcareous skarn which is distributed at the southeast contact between the Huoshenmiao pluton and the Sanchuan marble. The mineralization process can be divided into skarn and quartz-sulfide episodes. The skarn episode can be subdivided into skarn and retrograde stages, and the quartzsulfide episode can be further divided into four stages, namely, quartz-K-feldspar, quartz-molybdenite, quartz-pyrite and quartz-calcite.2. The Huoshenmiao pluton are composed of quartz diorite, monzo-granite and granite porphyry, and the formation ages of quartz diorite, monzo-granite and granite porphyry are 150.3±0.6Ma, 146.0±0.6Ma and 145.1±0.5Ma, respectively. The pluton belongs to I-type granite, and it results from acending magma formed by partial melting of different source regions. The quartz diorite stems from remelting of the enriched mantle, while the monzo-granite and granite porphyry are products of mafic magma derived from remelting of the enriched mantle mixed with felsic magma derived from remelting of the Taihua TTG.3. The formation age of the Huoshenmiao deposit is 145.7±3.9Ma, implying that it was formed in late Jurassic.4. Three types of fluid inclusion were recognized in the Huoshenmiao deposit, namely, aqueous two-phase, daughter mineral-bearing multiphase and CO₂-bearing three-phase. The homogenization temperatures and salinities of fluid inclusions vary in the range of 102^>600℃ and 0⁶2% NaCleqv, respectively. The ore-forming fluids are characterized by high temperature and medium-high salinity, belonging to H₂O-NaCl±CO₂±CH4 system.5. The δ¹⁸O_H2O values of the ore-forming fluids in quartz-sulfide episode were 2.3¹0.5‰ and the δDH2O values were-112‰ to-76‰, implying that the ore-forming fluids gradually evolved from magmatic to meteoric in origin. The δ13CPDB values of calcite were 0.4¹.2‰ and the δ¹⁸O_SMOW values were 5.5‰ to 6.0‰, and the δ34S values of sulfides ranged from 3.0‰ to 7.1‰, indicating that C and S in the deposit were magmatic in origin.6. Under the background of extension caused by subduction of the Izanagi plate beneath the Eurasian continent in the Late Jurassic, a large number of mafic magma and felsic magma were generated by partial melting of the enriched mantle and Taihua TTG, respectively. During magma mixing, plenty of Mo was provided to the magma chamber by the mafic magma. Then the mixed magma crystallized and a large amount of ore-forming fluids were released. During the ore-forming fluids ascent, multiple boiling and water-rock reaction occurred, resulting in the precipitation of Mo and formation of the deposit.