Spatial Regularities of Localization of Gold Ore Occurrences in the Yana–Kolyma Province

Abstract

To solve the problems of regional forecast within the Yana–Kolyma gold ore province, analysis of the spatial distribution of 2140 orogenic ore objects and their gold grades was carried out. Ore objects with >1 ppm Au are mapped on a scale of 1: 2,500,000, and areas of high mineralization density points are outlined in the sequence: general contour–contours around clusters of points with high Au grade–contours around proximal clusters of points–long axes of anisotropic contours. The curves obtained after the interpolation between the axes, with regard to the actual position of the ore objects, are interpreted as intersections of the recent topographic surface with the planes of faults that were active at the time of ore formation (ore-hosting faults). We propose to call the curves intersecting the known deposits “trends” (arched and linear). If no deposits have been revealed, the curves should be called “ore lineaments”, regardless of their curvature. The shape of the general contour around the gold ore occurrences and the distribution of ore objects within this contour permit outlining the Upper Indigirka (UID) and Central Kolyma (CKD) megadistricts. The geometry and spatial position of trends and ore lineaments are compared with the recent structural plan of the area, with geophysical fields, and with the existing ideas of the kinematic types of faults arising under certain geodynamic regimes of evolution of structures in the Yana–Kolyma province. It is suggested that the ore-hosting faults formed successively during the collisional interaction of the passive margin of the Siberian continent with the Kolyma–Omolon superterrane and during the formation of the volcanic arcs of the Okhotsk–Chukchi volcanic belt. Trends and ore lineaments can be correlated with the groups of structures of ore fields formed at the late collisional and subduction (post- collisional) stages of the area evolution. The trends and ore lineaments of NW orientation are attributed to the folded reverse faults and thrusts and to shears of different kinematics. At the postcollisional stage, the ore lineaments and trends of NE orientation formed in the zones of tectonomagmatic activity, subparallel to the strike of volcanic arcs of the Okhotsk–Chukchi volcanogenic belt. The distribution of clusters of gold ore occurrences and “empty” intervals between them along the strike of the recognized structures probably corresponds to the distribution of areas of extension and compression in the plane of the ore-hosting faults. The correlation among the trends, ore lineaments, and ore-hosting faults permits forecasting for the position and approximate size of new ore bodies within the Yana–Kolyma province. Prospective areas for a gold ores prospecting and exploration have been outlined on the extrapolated and interpolated extensions of the trends and at the sites of their intersection.