White mica

Muscovite or white mica has the formula KAl2(OH)2(AlSi3Oio). Since they are not... 

In metamorphic rocks, muscovite occurs in low-grade terrains of the regional metamorphism (albite-chlorite-sericite schists). It must be noted here that the term sericite identifies fine-grained white micas (muscovite, paragonite). 

Aii iamprophyres have been ciassified as sannaite iamprophyres, except an uitramafic damtjernite. The sannaite iamprophyres contain kfs, amp cai, cpx, phi, ap, pi, sodaiite, ms, ttn, ep, white mica, chi, zrn, and opaque phases. The coarse-grained damtjernite consists of phenocrystic phiogopite, with groundmass caicite, aikaii feidspar, and apatite. 

The phyllic alteration zone coincides with a subtle but consistent shift in the dominant AlOH peak in the short-wave infrared spectrum ( 2210 nm) to slightly lower wavelengths, consistent with an inner white mica-ferroan carbonate mineral assemblage. A preliminary analysis of hyperspectral data over the visible to near infrared range suggests that ferroan carbonates may be detected but not reliably quantified. However, TIR data allow calcite and ferroan carbonate to be distinguished, and may also detect increasing Fe content in ferroan dolomite as mineralized structures are approached. 

The volcaniclastic rocks hosting the Boomerang massive sulfide show a wide range of petrographic and chemical compositions. Petrographically the HW volcaniclastic rocks show increasing finegrained white mica (muscovite/sericite) development with proximity to the mineralized horizon. The abundance of these phyllosilicates enhances the development of more intense foliation in... 

Strong bleaching and alteration of host siltstones only occurs proximal (< 2 m) to the veins, whereas spot-bleaching occurs more distally (< ca. 10 m) and is commonly not spatially associated with quartz veining. Alteration in coarsegrained sedimentary rocks is subtle and is accompanied by an increase in sulfides (typically pyrite) along with chlorite+sericite (white mica) and carbonate. 

Synonyms Mica is a nonfibrous silicate occurring in plate form and includes nine different species muscovite is a hydrated aluminum potassium silicate also called white mica phlo-gopite is an aluminum potassium magnesium silicate also called amber mica other forms are biotite, lepidolite, zinnwaldite, and roscoelite... 

Figure 13.5. White mica in a regional metamorphic rock using the decoration method [5]. 

S. Tomura, M. Kitamura, and I. Sunagawa, Surface microtopography of metamorphic white micas, Phys. Chem. Min., 5,1979, 65-81... 

With the advent of stable isotope paleoaltimetry towards the turn of the millennium the stable isotope and tectonics communities have witnessed an increasing number of isotopic mineral proxies developed to address the long-term topographic histories of orogenic belts and continental plateaus. These proxies include calcite from paleosols (see for example Quade et al. 2007, this volume and references therein), fluvial and lacustrine rocks the phosphate and carbonate component of mammal teeth (Kohn and Dettman 2007, this volume and references therein), smectite and kaolinite from paleosols, weathered sediments and volcanic ashes (e.g., Chamberlain et al. 1999 Takeuchi and Larson 2005 Mulch et al. 2006a) as well as white mica from extensional shear zones and fluid inclusions in hydrothermal veins (e.g., Mulch et al. 

Cosca 2004 Mulch et al. 2005, 2006b). The utility of synkinematic white mica in mylonitic quartzite for paleoaltimetry is, therefore, based on the coupled stable isotope (lsO/lsO, D/H) and radiogenic isotope (40Ar/39Ar) record. 

The long time scales (104 to 10s m.y.) involved in deformation and synkinematic isotope exchange in white mica provide a robust, long-term average of meteoric water-rock interaction, characteristic for the time scales of major readjustments in surface elevation. Thus the hydrogen isotope record in recrystallized muscovite provides a direct link between the tectonic and fluid flow history in the shear zone and temporal variations in meteoric water composition due to changing surface elevation. 

Metallic, white, Marieburg, combined with white Mica. 

Di Vincenzo G., Ghiribelli B., Giorgetti G., and Pahneri R. (2001) Evidence of a close link between petrology and isotope records constraints from SEM, EMP, TEM and in situ Ar-40-Ar-39 laser analyses on multiple generations of white micas (Lanterman Range, Antarctica). Earth Planet. Sci. Lett. 192(3), 389-405. 

Dunlap W. J. (1997) NeocrystaUization or cooling Ar/ Ar ages of white micas from low-grade mylonites. Chem. Geol. 143, 181-203. 

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