Granitoids

The Yamizo Mountains are mostly occupied by Paleozoic-Mesozoic sedimentary rocks, mainly of Jurassic age (e.g., Sashida et al., 1982) with a small amount of intrusive granitoids of unknown ages. The Paleozoic-Mesozoic sedimentary rocks have been called the Yamizo Formation (Kanomata, 1961). It is composed chiefly of shale, sandstone, alternating beds of shale and sandstone, and a small amount of limestone and chert. The succession of the geologic units and geologic structure of the Yamizo Formation have been left pending due to complex structure such as upturned beds (Kasai, 1978) and submarine land sliding (Aono et al., 1985). 

Gold-quartz veins ranging in width from several centimeters to several ten centimeters are situated in shale and/or sandstone of the Yamizo Formation and rarely in granitoids. The strike and dip of the veins are various. For example, the veins of the Kuryu, Shiozawa, and Daigo deposits strike N40°W, N20-30°W, and N30°E, respectively, and dip 60°E, 30-50°W, and 20°W, respectively. 

Ishihara, S. (1981) The granitoid series and mineralization. Econ. Geol., 75th Anniversary Volume, 458-484. 

Lowenstem et al. (2000) used the same approach to date several zircons found in granitoid xenoliths ejected by Medicine Lake volcano (California) during two eruptions, 1065 and 2000 years ago. The ages obtained at 29 and 90 ka are thought to represent previous intrusive episodes in this magmatic system. 

Karacik, Z., Yilmaz, Y., Pearce, J.A., Ece, O.l. 2008. Petrochemistry of the south Marmara granitoids, northwest Anatolia, Turkey, International Journal of Earth Sciences, 97, 1181-1200. 

Table 5.32 Compositions (in weight %) of natural pyroxenes (samples 1-5 from Deer et al., 1983 samples 6 and 7 from Bonatti et al., 1986) (1) enstatite from a pyroxenite (2) ferrosilite from a thermometamorphic iron band (3) hedembergite (4) chromian augite from a gabbroic rock of the Bushveld complex (5) aegirine from a riebeckite-albite granitoid (6) diopside from a mantle peridotite (7) enstatite from a mantle peridotite. ...

Figure 5.71A shows univariant equilibrium curves for various molar amounts of ferrous component in the orthopyroxene mixture. The P-T field is split into two domains, corresponding to the structural state of the coexisting quartz (a and j3 polymorphs, respectively). If the temperature is known, the composition of phases furnishes a precise estimate of the P of equilibrium for this paragenesis. Equation 5.277 is calibrated only for the most ferriferous terms, and the geobarometer is applicable only to Fe-rich rocks such as charnockites and fayalite-bearing granitoids. 

Kotelnikov A. R., Bychkov A. M., and Chernavina N. I. (1981). Experimental stndy of calcium distribution in granitoid plagioclase and water-salt fluid at 700°C and Pn = 1000 atm. 

ISHiHARA, S. 1988. Rhenium contents of molybdenites in granitoid-series rocks in Japan. Economic Geology, 83, 1047-1051. 

The granitoid pluton is mostly massive, with some isolated off-shoots of the pluton in the east show foliation in the NW-SE direction with moderate dips towards SW (Fig.1), which is parallel to the schistosity of the country-rock metapelites. Pegmatites and pegmatitic quartz veins occur in metasediments, spatially associated with the granites. 

In the CIPW normative Ab-An-Or diagram, the Sargipali granitoid is a granite (Fig. 2a). This granite is... 

Fig. 2. Plot of Sargipali granitoid in (a) CIPW normative Ab-Or-An diagram (after Barker 1979), and (b) Shand s classification of granites, based on Al-saturation index. Symbols filled circles - massive granite, open circles - foliated granite.

Fig. 3. Sargipali granitoid showing (a) updated Rb vs Y+Nb discrimination plots (after Pearce 1996) and (b) CN REE systematics. Symbols are same as in Figure 2...

Fig. 1. Location map of the Collahuasi district (outlined) and geographic distribution of the outcrops of main igneous units of the Collahuasi Group in northern Chile. Ages for granitoids from the region are also shown (from Munizaga et a/. 2008 and references therein).

Petrologic, geochemical characteristics, and age of skarn-related granitoids at the Mactung Tungsten Deposit, Yukon, Canada... 

Keywords Yukon, Mactung, Geochemistry, Geochronology, Granitoids,... 

Rb and Sr/ Sr ratios equal to or higher than those of coexisting plagioclase (White et al. 2005). Sr content in the calcite of the Chehelkureh granitoids is relatively low. The ubiquitous nature of accessory calcite documented in this study implies late-magmatic growth or subsolidus replacement of igneous phases. 

Maanijou, M., Lentz, D., Rasa, I., Aletaha, B. 2006. Petrography, Geochemistry and Geotectonic Environment of Arc-Related Granitoids in the Chehelkureh area. Southeast Iran Implications for the Formation of the Polymetallic Ore Deposit in the Region. 1 iAGOD, Moscow, 4 p. 

White, A.F., Schulz, M.S., Lowenstern, J.B., ViviT, D.V., Bullen, T.D. 2005. The ubiquitous nature of accessory calcite in granitoid rocks Implications for petrogenesis. Geochimica et Cosmochimica Acta, 69, 1455-1471. 

Longstaffe, F, Smith, T.E., Muelenbachs, K. 1980. Oxygen isotope evidence for the genesis of Upper Paleozoic granitoids from southwestern Nova Scotia. Canadian Journal of Earth Sdences, 17, 132-141. 

Surface exposures of the San Miguel skarn deposit occur isolated over a 4000 m area, surrounded by intruding Proterozoic granitoid outcrops. The San Miguel skarn is mainly hosted by the Precambrian marbles of the Buenos Aires Complex. 

Granitoids are tonalitic to granitic in composition they have granular... 

The northern part of the Bendigo-Baiiarat zone consists of an Ordovician fiysch sequence which has been complexly deformed and intruded by late Devonian granitoids. In the south-western part of the study area Tertiary basalt overlies much of the Ordovician sedimentary sequence. Practically all known goldfields and mineralized zones have been discovered in areas where Ordovician sedimentary rocks crop out. 

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