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boundaries are chaotic and surrounded by quartz clusters. Many feldspars have lost their
euhedral shape due to “invading” quartz. Horblendes are altered. Some microclines are
perthitic and myrmektite is found in some plagioclases. 46% of the opaques are situated far
from biotite, 37% adjacent and17% as inclusions in biotite. The average size of opaques is 0.1
mm and they are round to idiomorphic in shape. There are no convincing examples of Feleaking opaques in this thin section. Heavy iron leakage is most often related to weathered
biotites (Fig. 12.). Many biotites have lost their optical properties.
Fig. 12. Iron leakage from weathered biotite. (a) Backscattered electron image of biotite. Clear quartz grains to
the right and plagioclase to the left. (b) Mapping image showing Fe concentration. Pictures from Granite 6.
Granite 2
Grain size: 3-6 mm
Crack width: up to 0.04 mm
Accessory minerals of significant concentration: epidote, magnetite, monazite, xenotime and
amphibole (unconfirmed).
This rock is the only fresh rock apart from the Bohus granite included in this study. The
sample is pictured together with the Bohus granite in (Fig. 13.) for comparison. The Bohus
granite has a much lower crack density than Granite 2. The cracks have a very distinct
orientation in this rock with a less distinct crack orientation perpendicular to it. Long, wide
and connected cracks in quartz are very typical features in this sample. There are wide
hydrothermally mineralised cracks in the dominant crack orientation which is filled by
sericite. The quartz grains are rather big aggregates and they are connected throughout the
rock. The rocks show many mineralogical similarities with the Bohus granite such as
saussuritised plagioclase (replacement of plagioclase by epidote), chloritised biotite and a
significant amount of Rare earth element mineral inclusions in biotite. Granite 2 has the
second highest concentration of light rare earth elements. Biotites are non- to partly
chloritised and have a lot of inclusions, including magnetite, monazite, Mn-ilmenite, apatite
and zircon. 48% of the opaques are situated adjacent to biotite, 28% far from biotite and 24%
as inclusions in biotite. The average size of opaques is 0.1 mm and they are usually euhedral.
A few microclines are perthitic. No sulphides were found using reflection microscopy.
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