滑坡構造的野外和遙感證據及其對哥倫比亞祖母綠開採的隱示

Abstract

The Colombian emeralds are well-known green gems, because of their unique characteristics, quality of color and sizes. Colombian Emeralds, located in the Eastern Cordillera, have under-ground mining in various locations. Separated by approximately 130Km is located the Eastern Emerald Belt (EEB) and the Western Emerald Belts (WEB), in a general context they share chemical and tectonic similarities, but, with a complex tectonic evolution. The geology of emerald and tectonic configuration is composed of disharmonic structures series, e.g., thrusted and folded areas. Current and past mining in these deposits created mines, more than a few tens in WEB, distributed in three districts, Muzo, Cunas, and Coscuez. Based on field surveys into those mines, we observed paths that suggest the location of mines in slumps or landslide areas (slope deformation), which are characterized by matrix-supported structures. Block sizes vary from centimeters to hundreds of meters. Types of blocks include black shale, mudstones, limestones, calcite-rich veins with emeralds, stratiform-pyrite, shale, hydrothermal hydraulic breccia and albitites. Most of the emeralds occur in calcite veins that suddenly cross-cut with no relationship of factors (faults, discontinuities, lateral continuity). In an attempt to explain these, a new concept called Slope Tectonics is applied, which identifies slope induced deformations that were initially related to a pure tectonic origin. We associate present-day exte-rior slope deformations with the structures observed inside the tunnels. These observations used remote sensing techniques (DEM, LANDSAT,) and geomorphometry. The WEB has slope deformation areas correlated with emerald mines. However, the relationship between present-day slope deformation and ancient deformation inside mines could not be veri-fied. These findings could be useful for further exploration, research projects of emeralds, and general mineral deposits