TITLE:
Structural Controls of the Coastal Bujuru and Retiro Heavy Minerals Deposits in Southern Brazil
AUTHORS:
Bruno Silva da Fontoura, Adelir José Strieder, Iran Carlos Stalliviere Corrêa, Paulo Rogério Mendes, Aureliano V. Nóbrega
KEYWORDS:
HM Placer Deposits, Gravity-Driven Deformation, Structural Traps
JOURNAL NAME:
Open Journal of Geology,
Vol.14 No.12,
December
10,
2024
ABSTRACT: This paper shows new results for Bujuru and Retiro HM deposits geological control, located in the Coastal Plain of the Rio Grande do Sul state (Brazil). Ground Penetrating Radar (GPR), drillholes and fieldwork were applied to investigate deformational structures that control Holocene sediment deposition and the HM deposits accumulation. The Bujuru and Retiro HM deposits were developed as a consequence to deformational traps (synthetic and antithetic normal faults). Mechanical subsidence and hanging-wall rotation, instead of sea level changes, are the main controlling mechanism for structural placers development that leads to existing HM deposits. Based on listric fault displacement and sedimentation rates, it is possible to distinguish three stages of lagoonal deposition, and two main episodes of HM accumulation. The preliminary HM concentration episode is due to sediment reworking from Pleistocene footwall escarpment and from a Pleistocene structural barrier developed in the hanging-wall oceanward (LFS 6). The second HM concentration episode is characterized by TDS and TD (LFS 5) developing upon a brachyanticline built due to the progressive deformation of the hanging-wall that includes previous Holocene lagoonal radarfacies. The TDS and TD are a sedimentary barrier and migrate inland due to NE onshore winds that also accumulate over the structurally controlled lagoons.