Dolerite intrusions near the Norwegian border have produced alteration zones in contact with clastic sediments and basalt. In the clastic rocks, mainly sandstones, the assemblage is epidote + chlorite + phengite + calcite + sphene, whereas in the basic igneous rocks it is epidote + pumpellyite + quartz + or - calcite + or - prehnite + or - actinolite. The epidote is Fe-rich with Fe/(Fe + Al) = or <0.43; pumpellyite ranges from the Al-rich to the Fe-rich variety. The occasional prehnite has relatively low Fe (FeO = or <1.9%) and high Mg(MgO = or <2.3%). An allanite is also reported (Ce2O3 13.7%). The formation of epidote in the sandstones is mainly related to the reaction of Ca-Fe-rich hydrothermal fluids with interstitial illite and detrital feldspars under conditions of high fO2 and 250-300oC.-R.A.H.
|Number of pages||18|
|Journal||Neues Jahrbuch fur Mineralogie, Abhandlungen|
|Publication status||Published - Jan 1 1986|
ASJC Scopus subject areas
- Geochemistry and Petrology