Numerous massifs of the Late Paleozoic leucogranites and quartz syenites of the Zaza complex are confined to the central, southern and south-western part of the Angara-Vitim batholith. Geological relations indicate the younger age of the Zaza granites. However, time intervals of their formation are in fact overlapped by U-Pb geochronological data (Tsygaankov et al., 2007 and bibliography). Mafic microgranular enclaves (MME) that occur both in quartz syenites and leucogranites are specific of the Zaza complex granitoids. Such enclaves are usually considered as feature of contrasting magma mixture, however, MME systematic study has not been carried out in the present case. In addition, the combined basite-aplite dykes and bodies of synplutonic basites that directly testify to coexistence and mixture of acid and basic magmas are present in some massifs. The Shaluty pluton that localizes 25 lm south of Ulan-Ude town belongs to such massifs (Fig.5, page 11).

The Shaluty massif (Litvinovsky et al., 1995) represents a part of larger Late Paleozoic pluton that is dismembered into a number of isolated, various size bodies by the younger granitoids. The area of the Shaluty massif is near 120 km². It consists of quartz syenites and leucocratic granites that correspond to two successive phases of introduction. Quartz syenites significantly prevail over leucogranites and are intruded by the combined quartz syenite-basic and aplite (leucogranite)-basite dykes and gabbroids. The latter form several separate bodies that are possibly protrusions of single massif.

The combined dykes are exposed both in rock outcrops of the Selenga River left bort and 200 m railway hollow near Old Shaluty village (Fig.6, page 12). Two various age groups of dykes are differed characterized by different composition of the cementing salic material: quartz syenite-basic dykes (SBD) and aplite (leucogranite)-basic ones (ABD). The dykes of Group I localize within quartz syenites and are confined to contacts of these rocks with the intruding gabbroids. The combined dykes of Group II are younger, and they crosscut both quartz syenites, gabbroids and syenite-basic dykes, and granites of phase II (north termination of Shaluty settlement). The combined dykes usually occur by series in observable length from first tens to 300 m and thickness from 15-20 cm to 4 m.

The internal structure of both type dykes is similar. The included basic enclaves (Fig.7, page 13) are irregularly distributed, locally, the combined dykes are transformed in pure quartz syenite or aplite ones that are almost free of basic material. Basic inclusions vary in size from 1-2 cm to 2 m in cross section. Lens-like, fusiform, irregular, extended inclusions that are oriented due to strike of dikes occur not rarely in some SBD. The cementing salic material is heterogeneous. Schlieren-like isolations and areas enriched in femic minerals and plagioclase are constantly noted in it. The combined dykes are characterized by all specific features of contrasting magma mixture products.

Basic inclusions (globules) have pillow-like, oval, rounded, lens-like form; festoony edges; quenched and porphyry varieties in marginal parts of large inclusions (more than 50-60 cm); areas with features of heterogeneous mixture viscous flow.

Within the Shaluty pluton, some gabbroid bodies that intrude quartz syenites of Phase I likely appear to be protrusions of the single massif. Signs of quenching are clearly observed at contact with quartz syenites in gabbroids. At the same time, signs of remelting, contamination and mixture are ubiquitously observed in quartz syenites that contain relict crystals of crystalline aggregates of coarse-grained origin (of host quartz syenite). The width of zone varies from 1-2 cm to 2 m, contours are distinct, however, the contact with coarse-grained quartz syenites is often gradational. Gabbros near contact with the zone of remelting represent an aggregate of pillow-like fragments divided by granitoid injections. The magmatic mixture that formed at contact with the basic intrusion, injected both the host quartz syenites and gabbroids themselves.

Quartz syenites and granites that compose the Shaluty pluton are macroscopically similar to each other. The quartz syenites are richer in femic minerals and composed by perthite K-feldspar (60-65%), acid plagioclase (12-15%), quartz (8-15%), biotite and edenite, with their amounts being nearly the same (3-4%). In granites, the part of quartz increases up to 35%, and that of plagioclase decreases up to 10-12%. Amphibole is not specific of granites.

Gabbroids of basite body inner zones are represented by middle-grained varieties with prism-granular, locally ophitic structure. Acid andesine, edenite and biotite with admixture of interstitional K-feldspar and quartz. Minerals of gabbro paragenesis itself are represented by corroded cores of zonal plagioclase (labradorite-bytownite), crystals of pyroxene and hornblende, almost completely replaced by edenite and biotite.

Irregular-grained and porphyry-like structure is more clearly observed in gabbros when approaching the contact with host quartz syenites. Plagioclase progressively enriches in albite component, parts of biotite, late salite, K-feldspar and quartz increase.

Basic rocks of inclusions in combined dykes are identical by fine-grained and porphyry-like gabbros of quenching and marginal zones in gabbroid bodies.

Quartz syenites of combined dykes and remelting zones do not differ by structural and textural peculiarities and mineral composition. They are heterogeneous rocks with great variations in ratios of rock forming minerals, microstructure and colour. Leucocratic varieties are most homogenous that are composed by prismatic K-feldspar, oligoclase, interstitional quartz and small amounts of biotite and edenite.

Chemical compositions of the Shaluty pluton most representative varieties, including gabbros and combined dykes are presented in Table 1. (pages 15-16)

Quartz syenites and granites belong to the typical subalkaline varieties, where even in granites, alkali contents exceed 8 mass %. In quartz syenites, content of petrogenic oxides is weakly correlated to silica. This dependence is more clearly observed in granites. Total direction of change in pluton rock composition in time indicates that granite magma could form during fractional crystallization of quartz-syenite melt. It is confirmed by character of rare element distribution (Fig. 8, page 14).

Quartz syenites of melting zones are differed by higher basicity that is caused by their contamination with basite material. However, “the purest” varieties slightly differ from rocks of subsrate, i.e. host quartz syenites.

Unaltered varieties practically lack among rocks of main composition that determines wide variations in their chemical composition. On the whole, with the increasing extent of gabbroids hybridization, contents of elements in them regularly approach those of the quartz syenites.