Abstract
The Buzwagi gold mine, found in the Neoarchaean Nzega greenstone belt of northern Tanzania; is underlain by mafic volcanic rocks which are associated with a massive body of ultramafic rocks that are considered to be cumulates. The mafic–ultramafic rocks association are cross-cut by ~2.71Ga grey TTG and ~2.67Ga pink microcline K-rich granites. The Buzwagi mine mafic volcanic rocks are Fe-rich tholeiites (MgO=3.59–7.67wt.%, Fe2O3=12.5–17.7wt.% and Mg#=30–56) that are characterized by flat REE (La/SmCN=0.78–1.12) and N-MORB like patterns except for moderate negative anomalies of Nb (Nb/Lapm=0.46–1.13) and Ta, Zr and Hf. The rocks exhibit sub-chondritic Zr/Hf ratios of 28.5–40.5 (average=32.6) and Ti/Zr ratios of 102–136 (average=124) and suggest that they are mantle-derived. Their La/Nb ratios of 0.85–2.10 encompass the range of oceanic ridge/plateau (La/Nb<1.4) and arc-like (La/Nb>1.4) basalts. The Buzwagi mine mafic volcanic rocks have been interpreted as products of 4–10% (average=5%) non-modal partial melting of the DMM source leaving a residual mineralogy comprised of olivine (57%), orthopyroxene (28%), clinopyroxene (13%) and spinel (2%). The DMM source was metasomatized by the slab-derived hydrous fluids in a back arc setting. This study corroborates previous evidence that crustal growth in the late Archaean Tanzania Craton occurred at convergent margins.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.