Composition of minerals (apatite, magnenite, ilmenite and others) as an index of conditions of layered massive ore formation in the laminated gabbro of Kusa intrusion (the Southern Urals)

Research subject. In this research, we carried out a series of mineralogical, petrological and geochemical studies to investigate ore zones present in the Kusa ilmenite-magnetite deposit located within the boundaries of a similarly-named laminated gabbro massif. Here, ore bodies occur at various intrusion horizons among laminated apogabbroid amphibolites of a different basicity. In the intrusion section, the composition of halogens (Cl, F) in co-existing fluid-bearing minerals (apatite, am-phibole, staurolite) was analyzed.Materials and methods. In order to investigate the composition of mineral samples, their polished sections were examined using an electronic-microprobe analyzer JXA-5. The content of petrogenic and microelement components (CRF and ICP-MS methods) in the rock and ore samples was determined using the facilities of the Laboratory of Physical and Chemical methods, UBRAS Institute of Geology and Geochemisty.Results. It is established that the content of Cl and F in the apatite, amphibole and staurolite under study, as well as the chemical composition of ilmenite, magnetite, and hombombite components, depend on the position of the ore bodies in the intrusion. Thus, the apatites from the near-ore rocks in the central part of the deposit showed the highest Cl concentrations of up to 4.1%, while those located in the near-contact parts of the intrusion demonstrated a much lower Cl content of 2%. The central ore-bearing zone having the maximal Cl content features the largest formation of ore bodies, which (including magnetite) contain higher amounts of Fe2O3, Cr and V The presence of fluid-bearing minerals (apatite, scapolite, etc.) with high chlorine concentrations of up to 2.44% is this deposit is established.Conclusions. The identified peculiarities of halogen distribution in the apatite of bipyroxene gabbro, as well as the inheritance of relations TiO2/FeO in bipyroxene gabbro, in massive magnetite-ilmenite ores and in near-ore rocks point to a single magmatic source of these formations.