In mineral exploration, a physiographic guide refers to using the landforms and terrain of an area to help locate potential mineral deposits. Physiographic features like ridges, fault scarps, and hogbacks can provide clues about underlying geological structures or mineralization zones. While not always a direct indicator of ore, these features can be valuable in narrowing down areas for further investigation.
According to (Gandhi & Sarkar, 2016), some physiographic guides are important and useful for mineral exploration purpose. In the lines below, we are going to share some of them:
Eminences and Depressions: the majority of significant deposits are found in pockets and low basins within mountainous terrain rather than spouting out at the surface in many mining districts. The physiographic features can provide both direct and indirect indications of the presence of ore. Although there may be useful indirect evidence, the direct indication of an ore body is its surface expression. Hogbacks and fault scarps are examples of geological features that are thought to be clues. The mineral outcrops are regarded as a noticeable feature in many areas. In several places, enormous quartz veins are visible as ridges, and the unsilicified rocks that lie between them have faded away. In contrast to the ridges of refractory quartz veins, more soluble beds (such as calcite veins) may develop distinct depressions. Because of the intimate network of stringers that are worn, broken, and dispersed, the weathering of soluble minerals and veins may produce a misleadingly large outcrop.
Oxidational Subsidence: depressions may form as a result of soft material erosion. Subsidences that resemble mine subsidences may also result from the removal of support caused by the ore bodies shrinking during oxidation.
Topography as a Guide to Iron Ore: while topography might serve as a guide in the search for ore, it frequently does not reveal the presence of ore on its own. Certain ore deposits are topographically associated with exposed surficial deposits or rock types. Large ore deposits can be located with the help of prominent topography features like mountain ranges and ridges. Large-scale reserves of bauxite and iron ore can be found all over the world, as is widely known. Topographic expressions will be helpful as a guide in discovering these mineral deposits because they must be vast in order to be commercially viable. Examples include hills, ridges, and ranges; iron ores in the Lake Superior region of the United States and Western Australia; and iron ores in the Indian states of Madhya Pradesh, Bihar, and Karnataka.
Physiographic Relations of Placer Deposition: physiographic events are essential to the buildup of placer deposits of heavy minerals such as gold, platinum, diamond, and others. Long-term weathering on mature terrain releases individual heavy mineral/metal particles from their host rocks, which are subsequently concentrated by sorting agents. The stream channel is the main ore locus. The gradient and velocity of the stream dictate the locations that are beneficial. An examination of physiography yields important placer-related information. Placer enrichment locations include oxbow lakes, terrace levels, rock bars, rock holes, and the mouths of side streams. Numerous placers are concentrated by wave action in beach sands (Australian alluvial rutile deposit; Indian beach placers (monazite, ilmenite, rutile, garnet); and deposits of cassiterite in Malaysian and Thai ocean sands. It is known that there are huge and abundant diamond reserves beneath the sea along the west coast of South Africa and Southwest Africa.
Reference
Gandhi, S. M., & Sarkar, B. C. (2016). Chapter 3—Reconnaissance and Prospecting. In S. M. Gandhi & B. C. Sarkar (Eds.), Essentials of Mineral Exploration and Evaluation (pp. 53–79). Elsevier. https://doi.org/10.1016/B978-0-12-805329-4.00010-7
