The role of airborne geophysics in the investigation of gold occurrences in the Itapetim Region, Borborema Province, Northeast Brazil

Laís Cristina Leite Pereira,Thais Andressa Carrino,Lauro Cézar Montefalco De Lira Santos

doi:10.1590/2317-4889201920190028

Laís Cristina Leite Pereira, Thais Andressa Carrino + Show 1 more

Open Access

https://doi.org/10.1590/2317-4889201920190028

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Abstract

Abstract We present a combined analysis of airborne geophysical data (magnetics and gamma-ray spectrometry) and field aspects of Itapetim lode gold district region, aiming to identify structurally deformed and hydrothermally altered zones, which are suggestive of gold mineralized sectors. The main geophysical lineaments are oriented in the NE-SW and E-W directions and display a clear correlation with the major gold-bearing structures in the region. In the magnetic maps, the key pathfinder for gold occurrences is their association with strongly magnetized areas positioned along the Itapetim Shear Zone and outer contour of Teixeira Batholith. In the field, such structures are materialized in protomylonitic and mylonitic rocks that present evidence of ductile and brittle deformation, whereas kinematic criteria are suggestive of a transpressional tectonic regime. In addition, the main radiometric pattern is characterized by K enrichment, which is correlated with a hydrothermal mineral assemblage dominated by quartz, potassium feldspar, and tourmaline. Based on the obtained data integration, we produced an integrative map and located ten new target areas of possible gold mineralization, which is correlative to other well-known lode deposits in Northeast Brazil and Africa.

Highlights

The occurrence and concentration of gold in the continental crust requires a combination of several geological processes, including specific tectonic settings, unique structural framework, and successive episodes of rock-fluid interaction (Groves et al 2003 and references therein)
Between the states of Pernambuco and Paraíba, gold mineralization is related to Itapetim gold district, which is considered the best-known example of Au mineralized quartz lodes hosted in supracrustal and granitic rocks of the central Borborema Province (Scheid & Ferreira 1991, Coutinho 1994, Santos et al 2014)
Associated rocks occur within wide developed shear zone corridors (Njome & Suh 2005) that probably extends from central Africa, across the Atlantic, into NE Brazil related gold-bearing rocks, such as those from Itapetim (Suh et al 2006, Takodjou Wambo et al 2018). This contribution presents an integrated analysis of airborne magnetic and gamma-ray spectrometric data of Itapetim gold district allied to the main field aspects observed in the mineralized areas

Summary

Introduction

The occurrence and concentration of gold in the continental crust requires a combination of several geological processes, including specific tectonic settings, unique structural framework, and successive episodes of rock-fluid interaction (Groves et al 2003 and references therein). Large-scale ductile shear zones are considered tectonic corridors for fluid percolation and subsequent metal concentration during metamorphism of oceanic rock sequences or devolatilization of the sediment wedge above the subduction slabs (Hronsky & Groves 2008, Groves & Santosh 2015). Between the states of Pernambuco and Paraíba, gold mineralization is related to Itapetim gold district, which is considered the best-known example of Au mineralized quartz lodes hosted in supracrustal (e.g. biotite-muscovite schist and biotite gneiss) and granitic rocks of the central Borborema Province (Scheid & Ferreira 1991, Coutinho 1994, Santos et al 2014). Gold-bearing rocks occur discontinuously along a 25 km-long area by 0.2 km wide (Wanderley 1999) and are considered a classical example of orogenic gold deposit (Coutinho 1994, Maia 2002, Almeida 2003)

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