In situ weathering of the Mesoproterozoic, hornblende- and biotite-rich Rønne granite atNygård kaolin pit provides a well preserved, Jurassic to Early Cretaceous saprolite section onBornholm. Fresh Rønne granite could be sampled in the approximately 800 m distant granitequarry at Klippeløkken. This study comprises petrographical and mineralogical thin section-,XRD- and SEM- analysis to distinguish the mode of primary mineral dissolution and secondaryclay mineral precipitation in the weathering profile. These analysis are based on sedimentarylogging, regular interval sampling, gamma ray- and fracture/joint measurements in fiveweathering profiles at the inactive Nygård kaolin pit. The weathering classification of saproliticlithology has been conducted according five facies, from fresh rock to highly weathered, friablesoil. The weathering sequence has been interpreted based on the mineralogical and petrographicalanalysis. Specific clay mineral abundance of kaolinite>>>chlorite>>smectite>illitestudied in the weathering profile have been used to interpret the depositional environment ofthe succession.Three main generations of weathering could be determined accordingly, 1. subaerialweathering, where original plagioclase feldspar, hornblende and biotite was dissolved andillite, smectite, illite/smectite mixed-layers and kaolinite clay minerals were formed duringEarly- to Late Jurassic. 2. Mineral formations during burial of the profile, are associatedwith the precipitation of carbonate concretions, foremost siderite, and authigenic chlorite in?Late Jurassic to Early Cretaceous. 3. Post-burial mineral reactions are mostly associated withoxidation conditions during seasonal changing groundwater percolation and the precipitationof hematite. Re-exposure and erosion of the overlying Rabekke Formation is suggested of LateCretaceous to Early Cenozoic time. Transpressional tectonics have led to fault reactivation andobduction of the southeastern margin of Bornholm.Corestone associations in the weathering section are well preserved and fracture/jointmeasurements revealed comparable strike directions with the adjacent granite quarry atKlippeløkken, suggesting only little to none tectonic impact between the two study localities.Tectonic stability, relatively low relief and prevailing humid and tropical climatic conditionscan be addressed as driving parameters for the argillization of thick kaolinite deposits duringthe Mid Mesozoic on Bornholm.The acquired results of this master thesis are used as comparison with other localities. Anexample of similar paleo-chemical weathering can be found at Ivö Klack (southern Sweden)also constituted by thick kaolinite deposits in the upper profile. In contrary, a recent weatheringprofile formed under more temperate arid conditions in NW Portugal displays arenization andkaolinite is replaced by gibbsite.As part of the Utsira Project, a collaboration of the University of Oslo and LundinPetroleum AS, it was the main focus of this study to provide lateral information of onshoreweathering profiles, that may be used as comparison to marine weathering successions foundin two drill cores from the Johan Svedrups field and the Edvard Grieg field in the North Sea.