9733773586

Krzysztof DZIEMIAŃCZUK ¹, Barbara WOJNAR²

TITANOMAGNETITE AND ILMENITE-HAEMATITE MINERALIZATION RELATED TO METAMORPHIC AND STRUCTURAL DEVELOPMENT OF A CRYSTALLINE COMPLEX OF SCHIST AND QUARTZITES: SOUTHERN PART OF THE STRZELIN GRANITOID MASSIF (SUDETES)

ABSTRACT: A ncw conccpi of the orc-mincralisation oręin in the mciamorphic rocks enclosing Variscan gramtoids of ihc Strzelin massif is presemed. The authors invcstigauons havc shown a polyphasc naturę of the metamorphic and tcctonic cvolution of orc-bearing schists and quartzites. The rocks in question developed from finc-gramed argillo-arcnaceous and silty sedimcnts containing local conccntrations of Fe-, Ti- and B-compounds which had previously precipitated from sea water. The sedimcnts were regionally mctamorphosed during the first phase of deformation (Di), which took place in the P-T conditions characterized by the orthoclasc + silhmanite paragenesis (K-fcldspar + Al^SiO^ isogradc. Winkler 1970). The solid Solutions of Fe- and Ti¹oxidcs were then generated in the conditions close to anatectic liquefaction. The processes of these oxides decompo-sition musi havc corrcspondcd to rctrogressive changcs which followcd the Di phase. Metamorphic recrystallization of two succcssiyc delormational evcnts (Di and Dj) h^s bcen only sliphtly and locally marked Thcrmal influence of the gramtoid mtrusion on its metamorphic manile was displayed in the rccrystallization of randomly oriented miner ais (sillimamte II. tourmaline. andalusite. orthoclase, micro-perthitc) as well as in the growth of large. regular crystals of Fe- and Ti-oxidcs The lattcr proccss resultcd from an interna! redistribution of the Fe- and Ti-ions. without any furlher materia! supply from the gramtoid magma itself.

Summary

INTRODUCTION

The present paper is intended to introduce a new concept of the origin of the ore mineralization in metamorphic rocks

enclosing the Strzelin granitoid massif. We consider the pre-vious trials to exp)ain the ore minerals origin madę by Olszyński (1972a, b) to be ovcrsimplified for the derived these

minerals from the contact influence of granitoid magma exclusively. Ore minerals being unquestionablc constituents

of mesoscopic tectonic structures, unequivocally show that their crystalhzation must have preceded the stage of Va-riscan granitoid emplacement. The elucidation of mineralization origin needs therefore the complicated tectonic and metamorphic evolution of Strzelin massif country rocks to be restored.

LOCATION OF THE ORE-MINERALISED ROCKS

The ore-bearing schists and quartzites are most extensi-vely exposed in the area located east of Romanów (Wyżna and Borowa hills, northern slopes of Gromnik hill; cf. fig. 1).

Mica-sillimanite-quartzitic schists and quartzites crop also out along a meridional zonę of exposures between Nowo-leska Kopa and Miecznik Hills. The northern and Southern

outerop areas of the ore-bearing schists and quartzites are separated from each other by the equatorially oriented Przeworno elevation. The uplift movements along this eleva-tion, combined with denudation processes, have caused the exposition of ore-bearing rocks in the core of Dobroszów unit (Oberc 1966). These rocks are immediately covered with

younger ones to the north and south from the elevation. The results of geophysical research works carried out in the Southern part of the investigated region (Maloszewski et al.

1970) seem to indicate the occurrence of ore-bearing quartzi-tes north of the summit of Nowoleska Kopa under a several tens of metres thick Quaternary cover.

1

Geological Institute, Lower Silesian Branch, ul. Jaworowa 19, 53-122 Wrocław.

2

Institute of Gcology, Polish Academy of Sciences, ul. Podwale 75, 50-449 Wrocław.