TY - JOUR
T1 - Zussmanite in ferruginous metasediments from southern central Chile
AU - Massonne, H. J.
AU - Hervé, F.
AU - Medenbach, O.
AU - Muñoz, V.
AU - Willner, A. P.
PY - 1998/12
Y1 - 1998/12
N2 - Zussmanite KFe13[AlSi17O42](OH)14, a modulated 2:1 layer silicate, has so far been found only in iron-rich metasediments from Laytonville, California (Agrell et al., 1965). A new occurrence is reported here from Punta Nihue north of Valdivia, Chile, in banded stilpnomelane-schists. These are intercalated in the 'Western Series', a complex of low-grade metamorphic rocks with local high-pressure, low-temperature overprint (e.g. blueschists). The rock contains conspicuous porphyroblasts of zussmanite of mm size and is composed of chemically distinct bands with the subsequent assemblages: (1) zussmanite-stilpnomelane-quartz, (2) siderite-quartz±stilpnomelane (3) apatite-stilpnomelane-quartz±siderite. The chemical composition of zussmanite, (K0.80Na0.05Ba0.01)(Fe11.29
2+Mg1.11Mn0.25Fe0.14
3 +Cr0.01Al0.19Ti0.01)[Al1.23Si16.77O42](OH)14, its optical properties and X-ray data correlate well with the Californian occurrence. Additionally, we present new IR data. In type (2) bands of fine-grained crystals of a K,Al poor mineral formed from siderite and quartz. Its chemical composition is close to that of zussmanite. A similar phase was also reported from Laytonville, California (Muir Wood, 1980). The rarity of rock-forming zussmanite can be explained by its occurrence in strongly Fe-rich and reduced rocks, as well as, by a possibly narrow P-T stability field.
AB - Zussmanite KFe13[AlSi17O42](OH)14, a modulated 2:1 layer silicate, has so far been found only in iron-rich metasediments from Laytonville, California (Agrell et al., 1965). A new occurrence is reported here from Punta Nihue north of Valdivia, Chile, in banded stilpnomelane-schists. These are intercalated in the 'Western Series', a complex of low-grade metamorphic rocks with local high-pressure, low-temperature overprint (e.g. blueschists). The rock contains conspicuous porphyroblasts of zussmanite of mm size and is composed of chemically distinct bands with the subsequent assemblages: (1) zussmanite-stilpnomelane-quartz, (2) siderite-quartz±stilpnomelane (3) apatite-stilpnomelane-quartz±siderite. The chemical composition of zussmanite, (K0.80Na0.05Ba0.01)(Fe11.29
2+Mg1.11Mn0.25Fe0.14
3 +Cr0.01Al0.19Ti0.01)[Al1.23Si16.77O42](OH)14, its optical properties and X-ray data correlate well with the Californian occurrence. Additionally, we present new IR data. In type (2) bands of fine-grained crystals of a K,Al poor mineral formed from siderite and quartz. Its chemical composition is close to that of zussmanite. A similar phase was also reported from Laytonville, California (Muir Wood, 1980). The rarity of rock-forming zussmanite can be explained by its occurrence in strongly Fe-rich and reduced rocks, as well as, by a possibly narrow P-T stability field.
KW - Chile
KW - Metasediments
KW - Punta Nihue
KW - Schist
KW - Zussmanite
UR - http://www.scopus.com/inward/record.url?scp=0032466734&partnerID=8YFLogxK
M3 - Article
AN - SCOPUS:0032466734
VL - 62
SP - 869
EP - 876
JO - Mineralogical Magazine
JF - Mineralogical Magazine
SN - 0026-461X
IS - 6
ER -