Platinum-and gold-bearing rodingites of the Ust’-Dep ophiolite block (middle Amur region)

Abstract

The Ust’-Dep ophiolite block, a part of the Selemdzha‐Zeya Belt, occupies an area of 350 km 2 and incorporates apoharzburgite serpentinite massifs intruded by numerous (>60) dikes of diabases and granitoids up to 100 m thick and more than 1 km long. Ophiolitic outcrops of this block make up a SW- to NW-trending band extending from the right bank of the Zeya River to the Gar River basin. Only small fragments of ophiolite massifs are preserved in spurs of the Tukuringr Ridge (Fig. 1). The Ust’-Dep and Gar protrusions in this area include dislocation zones with superimposed metasomatic alterations (development of listvenites and rodingites with gold mineralization). The majority of rodingite and listvenite occurrences are confined to outcrops of Lower Paleozoic‐Middle Cretaceous granitoid intrusions and dikes. Listvenites usually considered the source of placer gold are scrutinized in [1, 2]. However, data on the gold potential of rodingites in the Ust’-Dep block are lacking, although they are similar to rodingites in the Zolotaya Gora deposit (southern Urals) that was previously proposed as a holotype of the gold‐rodingite association [3]. Their similarity is manifested in the development of rodingites among listvenitized serpentinites. Therefore, the gold mineralization of Uralian rodingites is attributed to a younger process of listvenitization [4].