Carlin Trend Geologic Overview

Abstract

Abstract The Carlin trend is a 60-kilometer-long line of predominantly sedimentary-rock-hosted gold deposits, which has already yielded 477 tonnes of gold production from a total resource exceeding 2500 tonnes of gold. Deposits are hosted predominantly within sedimentary rocks deposited on the Paleozoic continental margin and subsequently compressed through Late Devonian continent-arc collision to form an allochthonous siliceous deep-water stratigraphic assemblage overlying an autochthonous shelf carbonate assemblage. A sequence of compressional, transpressional, and later extensional tectonic events has further shaped the geologic architecture. Gold mineralization is characterized by sub-micron sized “invisible” gold as discrete grains and incorporated within iron sulfides . Deposits are localized within rock volumes rendered sufficiently permeable by primary lithology, chemical alteration, or structural preparation. Alteration styles spatially associated with gold mineralization include decalcification, silicification, argillization, sulfidation, and introduction of the minerals barite and alunite and geochemically anomalous concentrations of As, Sb, Hg, Ag, and Tl. The age of gold mineralization is poorly constrained but believed to be Oligocene. While descriptive models for this type of deposit are well developed, genetic models remain strongly contested.