Molybdenum–copper–porphyry mineralization in the Pavlovich ore field

The article presents new data on mineral composition and geochemical features of molybdenum–copper–porphyry mineralization in the Pavlovich ore field in the Northern Priokhotye (northern coast of the Sea of Okhotsk), Magadan Region. The field adjoins the homonymous plutonic intrusions of the Alb-Cenomanian granitoids of the Priokhotye Plutonic Belt, intruded in the island-arc volcanic Middle-Jurassic rocks represented by mostly basalt, andesite and their tuff. The ore fold-like mineralization shows up as quartz–sulfide veinlets, with impregnations of molybdenite and copper minerals, and as widely spread zones of secondary quartzite and orthoclase. The structure of the ore fold composed of tonalite–porphyry and porphyritic granodiorite features a horizontal zonality of geothermal–metasomatic transformations: from metasomatic sericite–quartzite rocks in the center to propylite in the periphery. The ore-bearing mineralization represents mostly chalcopyrite, magnetite, chalcosine, bornite and molybdenite of two generations, including the earlier generation with fine-flake molybdenite grains rich with rhenium (to 2800g/t). The ore fold is opened in coastal cliffs 420–500 m high. The top of the fold contains a frank zone of hypergenic transformation of ore with chalcopyrite, malachite, azurite and chrysocolla with a general thickness of 50–70 m. The Pavlovich ore field is a complex ore field, with the main components of Cu and Mo accompanied with W, Te, Bi, Ag, Pb, Zn and sometimes Au. The authors distinguish conditionally three types of ore by its composition criterion: anomalous ore—Cu (9 %), Mo (0.8 %) and Ag (97 g/t); rich ore—Cu (1.16 %), Mo (0.29 %) and Ag (11 g/t); poor ore—Cu (0.2 %), Mo (0.02 %) and Ag (2.4 g/t). The composition of ore, the formation sequence and the geochemical indicators allow categorizing the mineralization as molybdenum–copper–porphyry type with silver. The mineralization parameters, similar to ore deposits in the Baim ore zone, make it possible to predict a commercial-value molybdenum–copper–porphyry deposit in the test field. The authors think the Pavlovich field is worth large-scale geological surveying and exploration.The study was carried out under the state contracts with the Federal Subsoil Use Agency, Contract No. 049-00018-22-01 dated 14 January 2022 Creation and Redaction of the State Geological Map, Scale 1:1 000 000, 3rd Generation, Using Sheets of the Russian Federation Territory in 2021–2023 (Sheets O-55 and O-56), and with the North-Eastern Integrated Research Institute FEB RAS, Contract No. 124051600003-4 Ore Content Criteria for Magmatic Rock Masses.