The Research On Genesis Of The Lamellar Ores Of The Luotuoshan Polymetallic Pyrite Deposit, Western Henan Province

The Luotuoshan polymetallic pyrite deposit is located at the north of Luanchuan Mo polymetallic ore concentration area of the western Henan Province. The orebodies mainly occur in the skarn of interbedded fault zone of Sanchuan Formation and Nannihu Formation of Neoproterozoic Luanchuan Group, controlled by NWW-trending interbedded fault zone. There are considerable debates about ore genesis in previous studies. The focus of controversy lies in it was formed from the exhalative sedimentary mineralization or Yanshanian magmatic hydrothermal metasomatism. The lamellar ores is considered as key evidence in exhalative sedimentary deposit, but it is also possible hydrothermal metasomatic genensis according to previous studies. Therefore, determining its metallogenic epoch and ore-forming materials resources are the most derect and effective way to solve these debats. In the spatial distribution, we found that the lamellar ores mainly occur between skarns and dense massive sulfide ores and some distribute in wall rock such as diopside feldspar and quartz hornfels, skarns and marbles by detailed field geological observation. The structure formed by alternate arrangement of different metallic minerals laminas and metallic minerals laminas and wall rock laminas. The geological features suggest that the lamellar ores replace skarns. The Rb-Sr dating is carried out for the lamellar ores, yielding an isochron age of 139.6 ± 2.6 Ma and suggesting the metallogenic epoch of Luotuoshan deposit was formed in early Cretaceous. Sulfur and strontium isotopes results show that δ34S values of the ores have a narrow range of +1.7‰ ~ +3.3‰, the tower-shaped distributional features is more obvious, and that the values of(87Sr/86Sr)i range from 0.709704 to 0.709943, with an average of 0.709823, which implies that ore-forming materials mainly originated from magma. The results of LA-ICP-MS show that the sphalerite formed on medium-high temperature condition,characterized by rich Fe, Mn, In, Co, while poor Ga, Ge and Tl, etc, and confirm that Fe, Mn, In, Co, Cd, Ga, Ge, Ag and Sn are present isomorphously, while Cu, Pb and Bi present as micro-inclusions of minerals(e.g. chalcopyrite, and galena) in spahalerite; The trace elements of pyrrhotite and pyriteare characterized by rich Co, while poor Ni, which confirm that Co, Ni, Ge and Asare present isomorphously, while Cu, Pb, Zn and Bi present as micro-inclusionsof minerals(e.g. chalcopyrite, galena and sphalerite). The Co/Ni ratios features of pyrhotite and pyrite indicate that this deposit is closely related to magmatic hydrothermal. Based on the above analysis, it is suggestive that the lamellar ores formed Mesozoic and belonged to magmatic hydrothermal genesis, further indicating the Luotuoshan polymetallic pyrite deposit is a skarn deposit. The work has a certain theoretical guidance meaning for the future to explore similar polymetallic pyrite deposit in this ore concentration area, even the whole western Henan Province.