Granodiorite

Muscovite mica formed as a primary mineral in pegmatites and granodiorite differs in physical properties compared to muscovite mica formed by secondary alteration (mica schist) (Table 2). The main differences are in flexibiUty and abiUty to be delaminated. Primary muscovite is not as brittle and delaminates much easier than muscovite formed as a secondary mineral. Mineralogical properties of the principal natural micas are shown in Table 3. The make-up of muscovite, phlogopite, and biotite are as follows ... 

Sheet Mica. Pockets of mica crystals ranging in size from a few square centimeters to several square meters are found in pegmatite sills and dikes or granodiorite (alaskite) ore bodies. In order to be used industrially, manufacturers must be able to cut a 6 cm pattern in the mica. "Books" of mica, ranging from 12.9 to 645 cm or more, are cut from the crystals. The books can be punched into various shapes and spHt into thicknesses varying from 0.0031 to 0.010 cm (12). The highest quaUty micas maybe used in aerospace computers, and those of lower quaUty find use as insulators in electrical apphances. 

The soft weathered granodiorite and pegmatites can vary in color from white to pink, depending on iron content and type of feldspar present. The mica content of these deposits ranges from 6—15% and varies in particle size from tiny (<44 specks to thumbnail size. Large books of mica that weigh several hundred kilograms have been found in these deposits. 

Flake Mica. Flake mica is mined from weathered and hard rock pegmatites, granodiorite, and schist and gneiss by conventional open-pit methods. In soft, residual material, dozers, shovels, scrapers, and front-end loaders are used to mine the ore. Often kaolin, quartz, and feldspar are recovered along with the mica (see also Clays Silicon compounds). 

Fig. 2. Flow sheet for the acid circuit processing and recovery of mica from weathered granodiorite ore. An alkaline—cationic circuit may be used by inserting a second conditioner containing lignin sulfonate, adjusting the pH to 8.0, and adding NaOH and DRL (distilled tall oil) fatty acid to the first...

Lateral zonation from a sericitic envelope to an intermediate argillic envelope is common in the porphyry copper deposits and vein-type deposits in granodioritic rocks... 

Porphyry copper deposits Cu-Mo disseminations in granodioritic porphyritic rocks Utah copper The Ruth, Nevada Climax, USA... 

Fig. 6.11. Calibration lines by using several CRM samples (S soil BHB-1, T Tibet soil GBW 8302, R river sediment CRM 320, Ga Gabbro MRG-1, A Andesite AGV-1, Gr Granodiorite GSP-1) and varying the sample weight (Zn 307.6 nm)...

In vertisols of Queensland and Tasmania derived on basalt, dolerite and alluvium, total Co is in the range of 7-70 mg/kg, but in soils derived on granodiorite, total Co is 3.5 mg/kg. In soils of the Adelaide and Southeast regions, Co varies from 1-30 mg/kg. 

In Queensland, soils on clayey sediments have 3-12 mg/kg total Mo, and mediterranean red soils on granodiorite and basalt contain 2-8.5 mg/kg Mo. In vertisols on dolerite in Tasmania, total Mo is 2.5-3.5 mg/kg. 

The amli pluton is subalkaline and calc-alkaline, and mainly diorite porphyry, granodiorite, quartz monzonite, and granite-porphyry in composition (Fig. 3). The metadiabase is alkali basalt in composition,... 

Petrographic observations were made on polished thin sections, for 313 outcrop samples. Average sample spacing was one sample per 1 km within a radius of 15 km or less from the known porphyry Cu-Mo deposits, and one sample per 2 km outside this area. Five rock types are distinguished in the district andesites, diorites, granodiorites, dacites, rhyolites and sandstones. Rhyolites and dacites dominate in the zone of known porphyry Cu-Mo deposits. Sandstones are much less common and were not studied. 

In diorite, granodiorite and andesites, propylitic alteration is characterized by... 

Rock type Granodiorites Diorites Andesites Chlorite, Epidote, Carbonates, Albite Chlorite, Epidote, Sericite, Rare carbonate veinlets... 

In addition to Au, a variety of Au-Sb, Au-Ag and Bi-Te alloys accompanied post-D2 arsenopyrite precipitation. Au and Bi-Te alloys are also locally concentrated in the biotite-rich margins of tonalite dykes that were contaminated by the host sediments. These alloys also appear to be concentrated within the HGA and are locally associated with disseminated scheelite and F-apatite. The latter also occur in late-stage veins that cross-cut weakly foliated granodiorite stocks that lie immediately beneath the HGA. A combination of BSE and CL imaging reveals that precipitation of these post-D2 sulfides and alloys occurred within a micro-porosity network that records dissolution-precipitation reactions... 

Nesbit, H.W. 1979. Mobility and fractionation of rare earth elements during weathering of a granodiorite. Nature, 279, 206-210. 

Three intrusions occur in the QB open pit and drill core. These consist of (/) Carboniferous diorite that was intruded by (/ /) Late Eocene granodiorite, and (///) later quartz-feldspar porphyry dykes of granodiorite composition. 

---