The origin of Patom Crater, East Siberia, from geological and geochemical data

Abstract

A multidisciplinary expedition of geologists‐ geochemists, geophysicists, and astronomers studied Patom Crater in Bodaibo District, north of Irkutsk oblast, in 2006. This paper presents new geological and geochemical data evidencing an endogenous origin of the crater. As was discovered, it represents a central ring structure with a cone of clastic material of limestone and other rocks. The structure appeared to have a zoned pattern created by consequent formation of early stage ring swell, late stage ring swell, ring trench, and central mound. Hence, it took quite some time to form Patom Crater, and it could not have been produced by a single event like meteorite collapse. The whole amount of analyzed stone samples within and around the crater gives no evidence of meteorite substance or any geochemical anomalies that could be related to it. Hypogene fluids and gases played important role in the formation of Patom Crater affecting the rocks of the cone. Along with oxidized fluids (H 2 O and CO 2 ), some reduced gases (CO, H 2 ) were found in the rocks of the crater. This points to a quite deep source of fluids. Patom Crater is not meteoritic, but was formed by endogenous processes, the most important being an outbreak of fluid substance from great depth, which led to the formation of a clastic cone.