Abstract
As the main part of the Indosinian metallogenic province in the eastern part of the Tethys metallogenic domain, Southeast Asia has experienced multiple stages of tectonic magnetic activities accompanied by the formation of rich mineral resources. However, due to the undeveloped economy, low degree of geological work, dense vegetation cover, and lack of obvious prospecting marks, traditional geological prospecting work in the area is not optimal. Consequently, the combination of high-precision geophysics and geochemistry has become an important method of looking for ore bodies deep underground in this area. The Nanpo gold deposit is a hydrothermal gold deposit that occurs in the Indosinian felsic volcanic rock body, and its mineralization is closely related to felsic magmatism. This study carried out comprehensive geophysical and geochemical exploration methods of soil geochemical survey, induced polarization (IP) survey, and audio-frequency magnetotelluric (AMT) survey. Based on the characteristics of geophysical and geochemical anomalies, geological inference, and interpretation, the integrated geophysical and geochemical prospecting criteria of the ore area have been determined: The large-scale and overlapping Au-Ag-Cu anomaly area in the host felsic magmatic rocks (mainly diorite, monzodiorite and granodiorite) is a favorable metallogenic area. Two anomalies, P1–H1 and P3–H6, with the best metallogenetic conditions and the deepest extensions of the known ore bodies, were further selected as engineering verification targets. After the study of the drill core, gold (mineralized) bodies consistent with the anomalies were found, indicating that the combined method is suitable for the exploration of mineral resources in this area, and the prospecting effect is good. At the same time, the metallogenic prediction shows that the deep part of the mining area still has great metallogenic prospects and prospecting potential. The characteristics of geophysical and geochemical anomalies and prospecting experience in the study area can provide references for the prospecting of hydrothermal gold deposits in the Luang Prabang–Loei structural belt.
Highlights
Over a long geological history of evolution, many different types of tectonic movements have taken place in Southeast Asia, forming various types and multi-stage magmatic superimposed magmatic tectonic belts
The soil geochemical survey had obvious concentration center, and the zonal center in many comprehensive anomalies delineated in the metallogenic favorable areas, such as orehosting strata and ore-controlling structures, and the abnormal area was large and the scale was good
Through comparative analysis of the induced polarization (IP) geophysical and soil geochemical anomaly areas, it was found that two anomaly areas, P1–H1 and P3–H6, with good overlap were in good agreement with the existing geological and metallogenic conditions, and they
Summary
Over a long geological history of evolution, many different types of tectonic movements have taken place in Southeast Asia, forming various types and multi-stage magmatic superimposed magmatic tectonic belts. Due to the underdeveloped economy of Laos and the lack of professional geological survey teams, the existing geological work in this area is low [14–18]. The complex natural conditions in the area, including extremely developed tropical rain forest, a few rock outcrops, strong weathering and inconvenient transportation in the forest area, greatly increase the difficulty of mineral exploration [19–25]. For these reasons, the traditional geological mapping or soil geochemical methods cannot be used to locate deep and concealed ore (mineralized) bodies alone. The prospecting work in this area can use the method of soil geochemical survey supplemented by geophysical survey
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