Geologia Croatica, Vol. 61 No. 1, 2008.
Original scientific paper
Si-P impure Al-Goethite Mineralization on the island of Dugi Otok (Central Adriatic, Croatia)
Branimir Šegvić
; Faculty of Mining, Geology and Petroleum Engineering
Boško Lugović
; Faculty of Mining, Geology and Petroleum Engineering
Neven Tadej
; Faculty of Mining, Geology and Petroleum Engineering
Vladimir Bermanec
; Department of Geology, Faculty of Science
Lovro Panjkota
; Faculty of Mining, Geology and Petroleum Engineering
Abstract
At the we stern seaward coast of the is land of Dugi otok, unusual goethite mineralization occurs as the in filling of a system of thin crevices in the Up per Cretaceous limestones of the Adriatic carbonate platform. Goethite is exceptionally well ordered and shows a variety of chemical compositions ranging from almost pure FeO·OH to Al-substituted composition accompanied by high Si and P impurity. The most characteristic textural type as asemblages are goethite
and coarse grained cal cite in composite aggregates. These aggregates contain Al-substituted goethite with metamorphic
silicate minerals embedded in the co re (black goethite), armoured by the XR D-pure, al most stoichiometric goethite (brown goethite). The geochemical and mineralogical features of the mineralization suggest an as cending solution
from a hid den me tamorphic source. We speculate that the source could have been activated by the thermal in flux linked to the Pliocene intraplate magmatism in the eastern segment of Adria.
Keywords
Al-goethite; stoichiometric goethite; crystalochemistry; endogenic origin; Dugi otok; Adriatic Sea; Adria microplate; Croatia
Hrčak ID:
24884
URI
Publication date:
2.7.2008.
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