Spatial distribution of rock uplift in the Bongar`a district (Peruvian Andes) and implications for the genesis of supergene ore deposits

Topography and river landscape morphometry of two hydrographic basins, the Utcubamba River and the Chiriaco River basins (Bongar & PRIME;a district, Amazonas region) allowed to determine the relationship between the irregular distribution of vertical motions (e.g., rock uplift) and the genesis of supergene Zn deposits. The latter derives from variable weathering of pre-existing carbonate-hosted Zn sulfides orebodies, in three distinct lo-calities: Florida Canyon, Mina Grande and Cristal. The research was carried out through the evaluation of the parameters such as elevation, local relief, swath profile, river longitudinal profiles and transformed river profiles (& chi;-long profiles), and slope/area analysis to derive the normalized channel steepness index (ksn). The NE-ward sharp increase in mean and minimum elevation coupled with a jump in the mean ksn values, suggests that the Chiriaco River basin has experienced more recent rock uplift than the Utcubamba River basin. In fact, the Utcubamba River experienced a long-lasting uplift, resulting in a rugged local relief and lowering the mean and minimum elevations, and exhumation and weathering of the Triassic-hosted sulfide mineral deposits at Florida Canyon. In the Chiriaco River basin, the younger uplift has promoted the weathering of the more surficial Jurassic-hosted Mina Grande and Cristal mineral deposits. The morphometric approach proved to be effective in recognizing fertile areas with near-surface orebodies also in regions characterized by distinct types of ore deposits.

Automated summary

The topography and river landscape morphometry of the Utcubamba River and the Chiriaco River basins revealed the relationship between vertical movements and the genesis of supergene Zn deposits. The research used various parameters to analyze the elevations, relief, profiles, and slope/area to determine the normalized channel steepness index. The results showed that the Utcubamba River basin experienced long-lasting uplift, while the Chiriaco River basin experienced more recent uplift.