Vozrozhdenie quarry, Leningrad Oblast, Russiai

Regional Level Types
Vozrozhdenie quarry	Quarry
Leningrad Oblast	Oblast
Russia	Country

The Gubanov Intrusion is a granitic intrusive body covering an area of about 20 km2 within the Wiborg Massif [18]. Vozrozhdenie facing stone deposits is its biggest exposure. Most researchers consider the intrusion as a body formed during a third phase of intrusion (after pyroxene-hornblende granites of phase I and ovoid biotite-hornblende wiborgites of phase II). Wiborgite is a regional term adopted by geologists in Finland, Sweden and Russia as a shorter synonym for the coarse-grained, ovoid-rich granites that are most common in rapakivi massifs. The Gubanov Intrusion consists of porphyritic biotite granites. Of note, the K-feldspar megacrysts (up to 30–40 mm) in the biotitic granites are idiomorphic with tabular habits rather than ovoids. These granites often display a trachytoid texture, especially near contact with host wiborgites. Feldspar ovoids, tentatively understood as xenocrysts trapped from wiborgites upon the intrusion of phase III, occur there as well. This conclusion is supported by the fact that the amount of ovoids in biotite granites decreases rapidly away from the contact.
The pegmatites from which the zircon sample was taken occur as 10–50 cm thick veined bodies cutting biotite granites mainly in the northern zone of the quarry. According to Prof. M.A. Ivanov (personal communication), they dip SW at 30–50°. They consist of K-Na feldspar (30–50 vol. %), plagioclase (An18–22, 15–20 vol. %), quartz (30–50 vol. %) and biotite (2–5 vol. %). They also contain albite, fluorite, titanite and muscovite; K-feldspar occasionally occurs as amazonite. Pegmatite bodies typically display symmetrically zoned structure (Figure 2b): near the contacts, they consist of fine-grained aggregate of biotite-quartz-feldspar composition, which is succeeded in its axial zone by coarse (up to 5 cm in size) feldspar and quartz crystals. Fluorite and amazonite, as well as miarolitic cavities containing idiomorphic quartz crystals, are confined to this zone.
Pegmatite veins are located inside the granites of phase III, near the contact with earlier granites of phase II. This suggests that pegmatites crystallized from the residual melt of granites of phase III, enriched with volatile and incompatible components. According to textural features, zircon crystallized simultaneously with the minerals of the central (giant-grained) part of the pegmatite vein—biotite and K-feldspar.

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References