Hyperspectral Remote Sensing Data and a Multi-proxy Investigation for Characterizing Mineral Resource Deposits in Alaska

Alaska image showing proposed hyperspectral survey areas. Areas of interest for proposed collection of imaging spectrometer data (hyperspectral remote sensing data) in Alaska. The four areas include a variety of deposit types and were designed to optimize data acquisition and ensure data collection in areas with potential mineralization. [click on image to view full size, 2.5 MB]

Alaska is considered one of the premier locations in the world for mineral exploration and for discovery of world-class mineral resources. However, Alaska is one of the most under-explored regions of the world and extensive ongoing efforts are underway to find areas with economic resource potential. In Alaska, both geologic mapping and minerals exploration are challenging for the same reasons: the state’s large size, limited transportation infrastructure, harsh climate, steep terrain, and an extensive cover of dense vegetation in the lower altitudes and snow and glaciers at the higher elevations. New strategies aimed at overcoming these obstacles are needed if Alaska’s mineral endowment is to be properly evaluated. The project's objectives are to characterize mineral composition and other surface parameters reflected in the acquired data. The synthesis of results from this investigation will enhance our understanding of the regional geology and be used to develop a predictive exploration model for the identification of precious, base and critical metal-bearing deposits in parts of the Alaska Range and Brooks Range. These results will illustrate how such remote sensing techniques can be applied to identification of resources in Alaska and similar remote regions of the world.

Pathfinder data development and integration

This work will provide the initial development of a framework for relating an area’s surface materials with its underlying geology. Geologic data, rock and sediment geochemistry, geobotany, geophysics, and multiple types of remotely sensed data will be compared in zones of mineralization.

Statewide Collaboration

The USGS will partner with the State of Alaska, the National Park Service, a number of exploration companies, Alaskan Native Corps, and other interested parties in order to complete this large-scale collection of airborne imaging spectrometer data. Areas of known deposits and occurrences will serve as test and validation sites. Collection areas will be prioritized based on the known or expected deposit type, size of the target, and accessibility, weather patterns, vegetation cover, and the interests of collaborators. The priority targets will include regions favorable for porphyry copper-gold deposits in the western and eastern parts of the Alaska Range, and for polymetallic volcanogenic massive sulfide deposits in the south-central Brooks Range.

Collection and processing of airborne hyperspectral data

The USGS plans to collect airborne imaging spectrometer data covering four areas of interest in the Alaska Range and Brooks Range, areas which include known large tonnage metallic mineral resources and associated broad alteration footprints. The airborne campaign and supporting field work for the calibration of and interpretation of the remote sensing data are planned for summer 2014. Complimentary remote sensing data from higher spatial resolution multispectral/radar sensors will be acquired, where feasible. New image processing and spectroscopic methods for mineral identification and mapping will be developed into publicly available software packages. In heavily vegetated areas, links between the underlying soil and rock properties and the spectral characteristics of vegetation cover will be investigated.

Data Integration and Synthesis

By collecting baseline data from sites of known mineralization, remote sensing data will be interpreted to indicate the links between surface and underlying materials. Researchers will integrate geology, geochemistry, geophysics, and botany at these sites to define spectral signatures of lithology, mineralization and associated environmental footprint. Markers from these interpretations will be compared to the remote sensing data and other existing geological data from throughout each of the four areas of interest to determine additional sites of high mineral resource favorability. Geological, geochemical, geophysical, and derivative maps based upon the airborne hyperspectral data will be developed for each of the four studied areas.