Layer-silicates in the contact zone between granite and serpentinite, jordanów, lower Silesia, Poland

Abstract

Chlorite belonging to subfamily C, vermiculite 2MB-VlI-meso, talc and a monoclinic amphibole were identified in rocks from a contact zone between highly tectonized granite and serpentinite at Jordan6w, Lower Silesia, Poland. K-saturated vermiculite readily produced a phlogopite-like structure 1M-I (3TA-IV) indicating trioctahedral mica to be its precursor. Spatial relations of the mineral assemblages were compared with published experimental data and used to produce a tentative model of the geological evolution of the rocks and minerals, which include four episodes of mineral development separated by three tectonic events.Materials from a small quarry near Jordan6w, in the eastern part of the Jordan6w-Gogot6w serpentinite massif (Lower Silesia, Poland) have been extensively studied for the last 100 years with particular attention on nephrite and calc-silicate rocks and minerals. The origin of these rocks and minerals is still controversial, however, and in the latest papers (e.g. Heflik, 1982) the rocks are considered to be rodingites or rodingite-like rocks developed at the expense of gabbroic dykes. Chlorite, smectite and talc, concomitant with calc-silicate rocks from Jordan6w, were assumed to be products of amphibole alteration and form a sequence: actinolite-,talc--,smectite-ochlorite (Heflik, 1967). This sequence seems to contradici conclusions on the evolution of the calc-silicate rocks from Jordan6w, especially those dealing with the remarkable influence of retrogression (Heflik, op. cit.). The purpose of this paper is to supply additional information on the genesis of the rocks from Jordan6w from detailed study of layer-silicates, which are susceptible to variations in physico-chemical conditions. MATERIALS AND METHODSRocks rich in layer-silicates (apart from the serpentinites) form veins up to 1.5 m thick, extending ~ 20 m (Fig. 1) and filling fissures in highly tectonized leucogranite, where they form flakes with minor acicular monoclinic amphibole. The composition of the veins changes gradually, amphibole becoming more abundant and, in the zone between the calc-silicate rocks and serpentinite, the veins consist mainly of the amphibole, with a minor admixture of other minerals in places. 1988 The Mineralogical Society

Interstratified vermiculite–mica in the gneiss–metapelite–serpentinite rocks at Hafafit area, Southern Eastern Desert, Egypt: From metasomatism to weathering

“…phlogopite to vermiculite proceeded slowly. Transformation occurred mainly through opening structure of mica minerals (Dubinska and Wiewiora, 1988). This was compensated by increase of Mg and H 2 O in octahedral and interlayer sites, respectively.…”

Scandian actinolite from Jordanów Śląski, Lower Silesia, Poland: Compositional evolution, crystal structure, and genetic implications

“…The research samples come from the thinner leucocratic zone. Here, the exocontact with the surrounding serpentinite is made of discontinuous and tectonically disrupted blackwall schist, from a few cm to ~1 m thick, containing vermiculite, chlorite, tremolite, and locally also talc (Dubińska and Wiewióra 1988;Dubińska and Szafranek 1990). It also hosts up to ~1.5 × 0.5 m large irregular bodies of nephrite, nephrite schists, and rocks transitional between nephrite and serpentinite as well as between nephrite and blackwall schist.…”

Heflikite, ideally Ca2(Al2Sc)(Si2O7)(SiO4)O(OH), the first scandium epidote-supergroup mineral from Jordanów Śląski, Lower Silesia, Poland and from Heftetjern, Tørdal, Norway

“…The latter occur usually as tectonic inclusions in sheared and sometimes also brecciated serpentinites and represent two genetic groups, i.e. boninitic and plagiogranitic rodingites (Dubińska, 1995(Dubińska, , 1997. In the Jordanów Śląski quarry, the serpentinites, built mostly of antigorite with minor chrysotile (Dubińska and Szafranek, 1990;Gil et al, 2015, 2020, andreferences therein), host two roughly NE-SW trending steeply dipping bodies of calc-silicate rocks: one ∼20-25 m, the other ∼5 m wide, traditionally called 'leucocratic zones'.…”

“…boninitic and plagiogranitic rodingites (Dubińska, 1995(Dubińska, , 1997. In the Jordanów Śląski quarry, the serpentinites, built mostly of antigorite with minor chrysotile (Dubińska and Szafranek, 1990;Gil et al, 2015, 2020, andreferences therein), host two roughly NE-SW trending steeply dipping bodies of calc-silicate rocks: one ∼20-25 m, the other ∼5 m wide, traditionally called 'leucocratic zones'. These rocks show diverse mineralogy dominated by grossular-rich garnet, zoisite and/or clinozoisite, epidote, prehnite and diopside, among others, and are believed to have formed from plagiogranitic-type protolith (e.g.…”

“…These rocks show diverse mineralogy dominated by grossular-rich garnet, zoisite and/or clinozoisite, epidote, prehnite and diopside, among others, and are believed to have formed from plagiogranitic-type protolith (e.g. Heflik, 1967Heflik, , 1982Majerowicz, 1984;Dubińska and Szafranek, 1990;Dubińska, 1995Dubińska, , 1997. Both rodingitic bodies are surrounded by discontinuous and tectonically disrupted 'blackwall schists', from a few cm to ∼1 m thick, containing mostly chlorite, vermiculite, tremolite, and locally also talc (Dubińska and Wiewióra, 1988;Dubińska and Szafranek, 1990).…”