Geochemistry and petrogenesis of intrusions at the Golden Pride gold deposit in the Nzega greenstone belt, Tanzania

Abstract

The greenstone sequence at Golden Pride gold deposit in Nzega greenstone belt of northern Tanzania is cross-cut by several intrusions whose geochemistry and petrogenesis is unknown. We present major and trace elements geochemistry of the Golden Pride igneous intrusions with the aim of constraining their petrogenesis and their ancient tectonic setting. The Golden Pride intrusions are geochemically categorized into two main rock suites: the granodiorites (which include the porphyries) and the lamprophyres (formerly intermediate intrusions). The granodiorites are characterized by SiO2 contents of 54.5–69.9 wt%, elevated MgO (1.22–3.59 wt%) Cr (up to 54 ppm), Mg# (35–55) pointing to a mantle component in the source. Compared to the TTG and adakites, the granodiorites are characterized by higher K2O (1.52–4.30 wt%), medium HREE (Gd/ErCN = 2.13–3.77) and marked enrichment in Ba and Sr (Ba + Sr = 819–2922 ppm) and are in these respects similar to Archean high Ba–Sr sanukitoids. The rocks...