Reconnaissance geochemical survey of the Farah Garan-Kutam mineral belt, Kingdom of Saudi Arabia

Abstract

Wadi-sediment samples were collected from 450 sites in a 580-km2 area (sample density 1.5 per km2) as part of an exploration program designed to assess the mineral potential of the Farah Garan -Kutam mineral belt and to evaluate mineralization at the Farah Garan ancient working (DGMR Project 3.03.10). Demagnetized panned-concentrate and sieved minus-80-mesh fractions were prepared from each bulk sample of approximately 5 kg. The fractions were analyzed for silver, arsenic, copper, lead, and zinc by atomic-absorption methods and for gold by an atomic-absorption graphite-furnace method.The analytical results for the panned-concentrate samples delineate 21 anomalies, and the results for the minus-80-mesh samples delineate 24. Of the latter, 14 are coincident with panned-concentrate anomaly areas, whereas 10 are uniquely defined. The analytical results of the panned-concentrate samples uniquely define two areas. Overall, the panned-concentrate samples yielded threshold values higher than the threshold values for the minus-80-mesh samples (for gold, 10 times higher), and delineate anomalous areas larger than those for the minus-80-mesh samples. This observation is consistent with the results of similar surveys elsewhere in the Arabian Shield, which indicate that panned-concentrate samples more effectively outline geochemical anomalies than sieved fine-grained samples.In the present survey, geochemical anomalies locate all the sites of mineralization known from previous work. The survey is therefore technically a success. However, a large number of these anomalies probably result from contamination of the wadi systems by metal dispersed from ancient mine workings, and this particular survey, overall, may be of limited value as a guide to the discovery of hitherto unknown mineralization. Nevertheless, the survey outlines two areas that may mark extensions to known mineralization, and a number of other areas in which no mineralization is known. Based on a consideration of the character of the bedrock geology, the value of each reported analytical result in relation to the respective element thresholds, and the number of anomalous samples that cluster in any given area, four areas are recommended for high-priority follow-up sampling.

Follow-up evaluation of fifteen geochemically anomalous areas and evaluation of four prospects in the Farah Garan-Kutam mineral belt, Kingdom of Saudi Arabia

“…In a separate study (Samater, 1989), panned concentrates obtained from 450 wadi-sediment samples collected throughout the Farah Garan district were analyzed for gold, silver, copper, lead, and zinc; anomalous values for these elements defined 21 exploration targets (Samater's targets are preceeded by an "A" on plate 1 and in the subsequent discussion). During the present study, traverses across 14 of these target areas were made mostly along wadi systems (plate 1) and all observed and suspected mineralized zones were chip sampled.…”

“…The sampled target areas are described individually below. All cited gold and silver values from pan concentrates are from Samater (1989). Study of frequencyverses concentration histograms yielded threshold values of 0.2 ppm for gold and silver.…”

“…The study involved two phases. During phase I, detailed investigations were undertaken of previously determined wadi sediment anomalies (Saleh, 1985;and Samater, 1989) in an attempt to determine the source of the anomalies. During phase II, chip sampling across four zones of sulfide mineralization was carried out; two of these zones were previously identified during regional mapping (A.A. Bookstrom and W.R. Vennum, unpub.…”