EVIDENCE FOR SYNTECTONIC GOLD MINERALIZATION AT GOWTU BERGI, EASTERN SURINAME, SOUTH AMERICA

A new gold deposit has been defined by core drilling and sampling of small-scale mining sites in the Merian Creek area of Eastern Suriname. Geologic and alteration mapping of saprolite exposures in mining sites and logging and petrography of core define a 2 km-long trend of vein-hosted gold mineralization at the Gowtu Bergi prospect. This is one of several subparallel mineralized trends.

All protolith rocks are metamorphosed to at least mid-greenschist grade. The up-section lithostratigraphy is (1) thin graded beds, (2) a discontinuous sandy argillite, (3) poorly-sorted litharenite and arkose, and (4) massively bedded well-sorted argillite and minor siltstone. Veins cut these protoliths and locally hydrothermally alter the wall rocks. Rare, thin post-mineralization dikes intrude the stratigraphic section. Locally, vein minerals include quartz, pyrite, pyrrhotite, feldspars, chlorite, sericite, carbonates, and minor molybdenite and chalcopyrite.

Multielement chemistry and multivariate statistical analysis of core show a correlation of gold with tellurium, bismuth, molybdenum, and cadmium which suggests a metaigneous or igneous source for mineralizing fluids. Factor loadings for host rocks suggest a felsic rather than mafic provenance.

The most common deformation is attenuation and thinning along the S₂ foliation planes, but locally, recrystallization, and cataclasis deform the protolith, earlier metamorphic textures, and synkinemetic vein-hosted gold mineralization. The stratigraphic sequence is folded into overturned folds verging to the southwest, with a wavelength of 50 to 150 m and amplitude of about 100 to 200 m. Fold limbs are sheared and highly attenuated, forming imbricate shear zones dipping 35 to 60 degrees northeast.

Pre-mineralization veining is mostly hosted by attenuated brittle-ductile zones within the finer-grained protoliths. Late veining fits a tension vein array (TVA) model and is symmetric with respect to fold axis and limbs and progresses from early TVA’s to late subvertical vein swarms within NW-striking shear zones.

Important potential ore deposits form where shear zones parallel highly-attenuated folds, especially anticlines. Micaceous minerals were preferentially removed by attenuation and early mineralized tension-vein material concentrated into the shear zone.