GROUND PENETRATING RADAR AND GIS IN FLUVIAL PLACER EXPLORATION, MAPLE CREEK, GUYANA

A total of 44 km of ground penetrating radar (GPR) survey line was collected at the Vannessa Ventures Ltd.’s Maple Creek diamond and gold placer property in Guyana, South America. Reconnaissance exploration indicated that a buried diamondiferous and gold-bearing deposit exists adjacent to and underlying Maple Creek. To date, traditional placer exploration has not embraced many of the technological advances successfully proven in other aspects of geoscience. In particular, new geophysical techniques integrated with GIS allow construction of a three-dimensional subsurface model and provide an exceptional tool for assisting in placer exploration.

Despite the technical challenges of conducting a GPR survey in the dense jungle, the data collected provided high quality imagery of a buried valley. The quartz-rich sediment allowed for exceptional depth penetration (>70 m) and high resolution imaging of the architecture of the fluvial valley fill sediments. The processed survey lines clearly imaged a number of discrete radar elements. These radar elements can be related to fluvial architectural elements and therefore, provide laterally extensive cross-sections of the valley fill sediments and the bounding surfaces. The most notable bounding surface is the 6th order bedrock-sediment interface that defines the paleo-bedrock surface. Utilizing GIS software, a three-dimensional model of the paleo-topography was constructed. Another regionally extensive surface is imaged near the top of the profiles and represents either a weathering contact or the sequence boundary between the fluvial valley fill sediments and ubiquitous surface sand. Other examples of architectural elements present in the GPR profiles are channels, barforms, as well as downstream and lateral-accretion macroforms. Extensive trenching in the study area confirmed many of the major reflectors and provided direct observation of some of the fill elements.

The processed survey lines, in conjunction with GIS imaging software enabled the construction of a three-dimensional model, recreating the bedrock topography and therefore delineating and imaging the paleo-valley. Armed with an accurate model of the paleo-topography, channel morphology, and an understanding the local stratigraphy, information such as resource estimates, exploration targets, and mine plans are possible.