The Bayankhongor Metal Belt (Mongolia): Constraints on Crustal Architecture and Implications for Mineral Emplacement from 3-D Electrical Resistivity Models

Matthew Comeau,Shoovdor Tserendug,Sodnomsambuu Demberel,Michael Becken,Erdenechimeg Batmagnai,Alexey Kuvshinov

doi:10.3390/iecms2021-09360

Matthew Comeau, Shoovdor Tserendug + Show 4 more

Open Access

https://doi.org/10.3390/iecms2021-09360

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Abstract

The Bayankhongor Metal Belt, a metallogenic belt that extends for more than 100 km in central Mongolia, is an economically significant zone that includes sources of gold and copper. Unfortunately, the crustal architecture is poorly understood throughout this region. However, it is known that the crustal structure strongly influences the development and emplacement of mineral zones. Electrical resistivity is a key physical parameter for mineral exploration that can help to locate mineral zones and determine the regional crustal structure. We use natural-source magnetotelluric data to generate three-dimensional electrical resistivity models of the crust. The results show that anomalous, low-resistivity zones in the upper crust are spatially associated with the surface expressions of known mineral occurrences, deposits, and mining projects. We thus infer that the development of the mineralization is closely linked to the low-resistivity signatures and, therefore, to crustal structures, due primarily to their influence on fluid flow. The low-resistivity signatures are possibly related to associated sulfide mineralogy within the host complex and to structures and weaknesses that facilitated fluid movement and contain traces of past hydrothermal alteration. Thus, the crustal architecture, including major crustal boundaries that influence fluid distribution, exerts a first-order control on the location of the metallogenic belt. By combining our electrical resistivity results with other geological and petrological data, we attempt to gain insights into the emplacement and origin of mineral resources.

Highlights

The mineral systems concept, whereby mineralized zones are seen as small expressions of a range of Earth processes, is recognized as the key to targeting new deposits and to interpreting ore genesis, through understanding the organizational framework of the system [1]
We investigate and discuss the geometry and extent of the features beneath the metallogenic belt and beneath the adjacent suture zone and ophiolite belt
The spatial distribution of mineral zones is known to be strongly influenced by the crustal architecture, which has an impact on the flow of fluids through the crust

Summary

Introduction

The mineral systems concept, whereby mineralized zones are seen as small expressions of a range of Earth processes, is recognized as the key to targeting new deposits and to interpreting ore genesis, through understanding the organizational framework of the system [1]. A large suture zone in central Mongolia, at the southern margin of the Hangai mountains within the Central Asian Orogenic Belt, is marked by the Bayankhongor Ophiolite Belt [4,5]. It is significant because it gives evidence for the closure of a paleo-ocean, and, it is believed to represent a major crustal boundary. To the south of the suture zone, metamorphic and volcanic provinces are identified [7] Distributed throughout this region are occurrences of gold and copper mineralization [8,9], which make up the Bayankhongor

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