Karvak Nusa geomatika

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Aero Magnetics Survey

High resolution aeromagnetic maps from data acquired by a total-field magnetometer reflect the underlying geology of the survey area. Such maps are invaluable tools for exploration Geologists working in all kinds of environments, whether forest, mountain or desert. They are also very important tools in the interpretation of structures and rock type distribution. Aeromagnetic surveys are rapid and relatively low-cost compared to other exploration techniques, which makes them very attractive as a reconnaissance tool in the early stages of an exploration project.

High resolution aeromagnetic surveys play a very important role in any exploration program. Improvements in magnetometer design and the introduction of real-time digital compensators now ensures very accurate data, which when combined with GPS, provides extremely detailed aeromagnetic and aeromagnetic derivative maps. Such highly detailed and accurate data and maps might indicate that areas that were previously flown using instrumentation and methods now considered obsolete should be reflown and mapped. In a minerals exploration program Aeromagnetic techniques may be used to do the following: • Map physical properties, including magnetic susceptibility and magnetic remanence • Map lithology, metamorphism, structure and tectonics • Map alterations and the enhancement or depletion of magnetite • Directly detect certain minerals, such as iron ore and pyrrhotite • Detect magnetic massive sulphide bodies, usually nickel or gold-copper-lead-zinc deposits • Detect kimberlite and lamproite intrusions • Detect chrome- or PGE-bearing ultramafic rocks • Detect tin-tungsten or rare-earths associated with granites • Geological mapping, including: ˗ Lithologic and structural mapping in weathered or covered areas ˗ Sedimentary basin geometry and structure, mapping intrasedimentary sources ˗ Regional studies for tectonic purposes (e.g. crustal studies) ˗ Exploration for favorable ore environments • Depth to basement mapping, including: ˗ Non-metallic mineral exploration ˗ Exploration for minerals associated with buried basement surfaces (e.g. gold and unconformity uranium)

Airborne Gammaray Spectrometry provides a direct measurement of the surface of the earth, with no significant depth of penetration. This at-surface characteristic allows us to reliably relate the measured radioelement contrasts to mapped bedrock and surficial geology and alteration associated with mineral deposits. All rocks, and materials derived from them are radioactive, containing detectable amounts of a variety of radioactive elements. A gamma-ray spectrometer is designed to detect the gamma rays associated with these radioactive elements and to accurately sort the detected gamma rays by their respective energies. Radiometrics, although used in oil & gas exploration, is more widely used in Mining exploration. Installed on a helicopters, and combined with other sensors, such as magnetics, a radiometric system is a very cost effective geological and geophysical mapping tool. For oil & gas exploration, a radiometric system may be used to detect subtle characteristic radiation patterns as indicators of subsurface hydrocarbon accumulations over petroliferous terrain. Potassium (K), uranium (U), and thorium (Th) are the three most abundant radioactive elements, occurring in various proportions in all rocks and soils. Their different chemical properties provide useful indicators of normal and anomalous chemical or mechanical (transport) processes. For geologic mapping and exploration purposes, the radiometric survey technique is usually considered and interpreted in geochemical terms. In appropriate areas, when used as a reconnaissance technique for mapping geology and for prospecting, the cost/benefit ratio for airborne radiometric surveying is nearly as good as that for airborne magnetometer surveying.

• An excellent tool for either oil & gas or mining exploration • Fixed-wing or helicopter mounted systems • Can be used alone or with other sensors, such as magnetics • Radiometric surveys measure variations in the natural radioactivity of an area • Modern spectrometers allow the detection of radioactivity at very low levels that were not previously detectable

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