METHOD TO DETERMINE PLATINUM-PALLADIUM AND COPPER-NICKEL METALLOGENIC TREND OF BASITE-ULTRABASITE LAMINATED MASSIF OF ARCHEAN CRYSTALLINE SHIELD Russian patent published in 2014 - IPC G01V9/00 

FIELD: measurement equipment.

SUBSTANCE: invention relates to methods of complex determination of metallogenic trend of basite-ultrabasite laminated massifs of Archean crystalline shields and may be used for separate prediction and searching for industrial objects of platinum-metal and copper-nickel mining materials. Substance: relation is established between genesis of laminated massif with geodynamic environment of rifting. Samples are taken, analysed, and substantial and mineralogical composition of petrographical varieties of rocks along the cut of the massif. Sections of most contrastive composition of magmatic series lamination and borders are identified. Concentration of isotopes U, Pb, Sm, Nd is measured in minerals and rocks of analysed samples. Absolute ages of rock varieties are calculated, as well as total duration of formation of laminated massif and value of an isotope indicator of massif rocks. Produced data is compared with indicator values of ages and duration of formation of laminated massif, and also values of the isotope indicator. A conclusion is made on prospectivity of the tested laminated massif for platinum-palladium or copper-nickel metallogenic trend. Additionally on the basis of data of geophysical research with account of the composition of depth crustal xenoliths and age of depleted matrix, they estimate the composition of the lower crust and the upper mantle for availability of the granulite-basite layer in the crust base. This layer creates favourable conditions for preliminary concentration of metals of the platinum group and is characterised by speed of longitudinal waves on the border of transition from the crust to the mantle Vp=7.7-7.1 km/s. Further they determine the mode of rifting development on the basis of the criterion of margin or continental type. At the same time formation of the basite-ultrabasite massif at the initial stage of the continental rifting testifies platinum-palladium metallogenic trend, and on the completing stages of rifting of margin type - copper-nickel metallogenic trend. Duration of the laminated massif formation is calculated with differentiation into ore and barren magmatic stages. Age intervals are determined for formation of ore mineralisation of platinum-palladium or copper-nickel metallogenic trend. Produced data is compared with indicator values of duration of massif formation with account of the fact that for platinum-palladium ore mineralisation with incidentally extracted Ni, Cu, Au, Co, Rh the indicator values of duration of formation are assessed as 2530-2420 million years, at the same time magmatic ore-bearing phases at the Baltic shield have the age of 2490±10 million years, 2470±10 million years, 2450±10 million years, and for the massif with copper-nickel mineralisation with incidentally extracted Co, S, platinum group metals, Se, Te, the indicator values of formation duration are in the range of 2200-1980 million years with the main ore phase, having the age of 1980±3 million years. The conclusion on prospectivity of the tested basite-ultrabasite massif for platinum-palladium or copper-nickel metallogenic trend is made with account of localisation of mineralisation of contact type in the lower series along the cut, mineralisation of rift type - at the border of series-megacycles with replacement of chemical composition of magmas, and mineralisation of offset type - in tectonic abnormalities in the thickness of country rocks.

EFFECT: higher efficiency and reduced resource intensity of definition of metallogenic specialisation of laminated massifs of basite-ultrabasites at early stages of geological survey of subsoil.

3 cl, 1 dwg