Exploration Methodology Using Morphology and Alloy Composition of Alluvial Gold: A Case Study from Quaternary Deposits o
- PDF / 9,061,970 Bytes
- 11 Pages / 595.276 x 790.866 pts Page_size
- 112 Downloads / 170 Views
Exploration Methodology Using Morphology and Alloy Composition of Alluvial Gold: A Case Study from Quaternary Deposits of the Nowshera District, Khyber Pakhtunkhwa, Pakistan Liaqat Ali 1 & Robert Chapman 2 & Mohammad Farhan 1 & Mohammad Tahir Shah 1 & Seema Anjum Khattak 1 & Asghar Ali 3 Received: 29 May 2019 / Accepted: 28 September 2020 # Society for Mining, Metallurgy & Exploration Inc. 2020
Abstract Alluvial gold is abundant in the Quaternary deposits of the Kabul and Indus rivers in District Nowshera, Khyber Pakhtunkhwa, Pakistan. Understanding the provenance of alluvial gold using morphology and elemental composition could be helpful in developing an exploration strategy of regional benefit. Detailed morphological studies of gold grains revealed high flatness index values which are indicative of a distal source. Compositional studies of 58 gold grains using SEM and EMPA showed broadly similar Ag ranges (1– 15 wt%) for each sample and occasional Cu values in individual gold particles to 0.4 wt%. Whilst the Ag profile is not diagnostic, the Cu values are compatible with derivation from either porphyry systems or ultrabasic rocks. The complex geology of the drainage catchments could host gold mineralization of other styles, but larger sample suites would be required to refine the current interpretation to establish whether particles which are simple Au-Ag alloys could be derived from orogenic or epithermal sources. This scoping study has demonstrated that the compositional and morphological studies of gold grains are useful in providing information regarding the nature and location of the source of placer gold in areas where there is limited information on the nature and location of in situ mineralization. Keywords Alluvial gold . Quaternary deposits . Morphology . Alloy composition . Provenance
1 Introduction Gold is primarily found in native form, usually alloyed with Ag, and in some cases with Cu, Hg or Pd, and the different alloy compositions of gold may be indicative of different sources of mineralization [1–4]. The alloy compositions of hypogene gold particles are retained by the detrital particles liberated during erosion and subsequently concentrated in fluvial environments. Consequently, the compositional characteristics of populations of placer gold grains may indicate the nature of the source mineralization and/or the genetic relationships between populations of gold particles collected at different localities [5]. This approach is particularly useful to
* Liaqat Ali [email protected] 1
National Centre of Excellence in Geology, University of Peshawar, Peshawar, Pakistan
2
Ores and Mineralization Group, School of Earth and Environment, University of Leeds, Leeds, UK
3
Department of Geology, University of Peshawar, Peshawar, Pakistan
understand the genetic nature of lode gold in a source area where there is limited information concerning in situ mineralization. Alluvial gold grains are malleable, and their morphology is progressively altered (flattened) during fluvial transport [6]. An ind
Data Loading...
