Aeromagnetometric Data Processing Revealing Emplacement History Of Granite Complexes: Lavras Do Sul Intrusive Complex And Jaguari Granite Intrusion Study Case (Rs, Brazil)

The Lavras do Sul Intrusive Complex (LSIC) is a<br>shoshonite- to alkaline type intrusion, while Jaguari<br>Granite Intrusion (JGI) shows just alkaline terms.<br>These both intrusions are close together in western<br>part of Sul-riograndense Shield. The aeromagnetic<br>data processing revealed two types of lineaments<br>around both intrusions (LSIC and JGI): i) regional<br>lineaments and ii) intrusion related lineaments; both<br>lineament types represent different shallow magnetic<br>source. Regional magnetic lineaments are related to<br>regional lithologies and deformational structures.<br>Intrusion related lineaments show a circular<br>distribution around both LSIC and JGI; they represent<br>shallow source, positive magnetic anomalies that are<br>caused by different types of mafic dikes: basaltic,<br>lamprophyric and/or kersantitic ones. There are also<br>felsic dikes around both LSIC and JGI, but they are<br>controlled by radial fracture system. As both LSIC<br>and JGI are circumscribed by circular dikes, at some<br>time during the magmatic event, they must have<br>evolved as a single magma chamber. Circular and<br>radial dikes also point to a large caldera structure that<br>must have evolved by multiple collapse episodes. The<br>development of a caldera structure is compatible to a<br>ballooning type emplacement mechanism for LSIC and JGI.