Metamorphic fingerprints of Fe-rich chromitites from the Eastern Pampean Ranges, Argentina
Por:
Colas, Vanessa, Subias, Ignacio, Maria Gonzalez-Jimenez, Jose, Proenza, Joaquin A., Fanlo, Isabel, Camprub, Antoni, Griffin, William L., Gervilla, Fernando, O'Reilly, Suzanne Y., Escayola, Monica F.
Publicada:
1 ene 2020
Categoría:
Earth and planetary sciences (miscellaneous)
Resumen:
Chromitites hosted in the serpentinized harzhurgite harzburgite bodies
from Los Congos and Los Guanacos (Eastern Pampean Ranges. north
Argentina) record a complex metamorphic evolution. The hydration of
chromitites during the renograde metamorphism, their subsequent
dehydration (luring the prograde metamorphism and the later-stage
cooling, have resulted in a threefold alteration of chromite: i) Type I
is characterized by homogeneous Fe3-- and Cr-rich chromite: ii) Type II
chromite contains exsolved textures that consist in blebs and fine
lamellae of a magnethe-rich phase homed in a spinet-rich phase; Type III
chromite is formed by satiable proportions of magnetite-rich and
spinet-rich phases with symplectitic texture. Type I chromite shows
lower Ga and higher Co, Zn and Mn than magmatic chmmites from
chromitites in suprasubduction zone ophiolites as a consequence of the
redistribution of three elements between Fe3--rich non-porous clunmite
and silicates during the prograde metamoiphism. Whereas, the spinel-rich
phase in Type III chromite is enriched in Co, Zn, Sc, and Ga, but
depleted in Mn, Ni. V and Ti with respect to the magnetite-rich phase,
due to the metamorphic cooling from high-temperature conditions. Th,
pseudosection calculated in the fluid-saturated FCr/sfACaSH system, and
contoured for Cr# and Mg#, allows us to constrain the temperature of
formation of Fr2--rich non-porous chmmite by the diffusion of magnetite
in Fe2--rich porous chrornite at degrees C and 20 kbar. The subsequent
dehydration of Fe3--rich non-porous chromite by reaction with amigo ire
and chlorite formed Type I chromite and Mg-rich olivine and pyroxene at
>800 degrees C and 10 kbar. The ultimate hydration of silicates in Type
I chromite and the exsolution of Type II and Type III chromites would
have started at similar to 600 na These temperatures are in the range of
those estimated for ocean floor serpentinizalion (<300 degrees C and <4
kbar), the regional prograde metamorphism in the granulite fades (800
degrees C and <10 kbar), and subsequent retrogression to the amphibolite
fairies (600 degrees C and 4-6.2 kbar) in the host uhramalic rocks at
Los Congos and Los Guanacos. A continuous and slow cooling from
granulite 10 amphibolite Facies produced the exsolution of spinet-rich
and magnetite-rich phases, developing sympleditic textures in Type III
chromite. However, the discontinuous and relatively fast cooling
produced the exsolution of magnetite-rich phase blebs and lamellae
within Type II chromite. The P-T conditions calculated in FCrMACaSH
system and the complex iextural and geochemical fingerprints showed by
Type I, Type II and Type III chromites leads us to suggest that
continent-continent collisional orogeny better records the fingerprints
of prograde metamorphism in ophiolific chromitites.
Filiaciones:
Colas, Vanessa:
Univ Nacl Autonoma Mexico, Inst Geol, Ciudad Univ, Coyoacan 04510, Cdmx, Mexico
Subias, Ignacio:
Univ Zaragoza, Dept Ciencias Tierra, Pedro Cerbuna 12, Zaragoza 50009, Spain
Maria Gonzalez-Jimenez, Jose:
Univ Granada, Dept Min & Petrol, Fac Ciencias, Ave Fuentenueva S-N, Granada 18002, Spain
Proenza, Joaquin A.:
Univ Barcelona, Dept Mineral Petrol & Geol Aplicada, C Marti & Franques S-N, Barcelona 08028, Spain
Fanlo, Isabel:
Univ Zaragoza, Dept Ciencias Tierra, Pedro Cerbuna 12, Zaragoza 50009, Spain
Camprub, Antoni:
Univ Nacl Autonoma Mexico, Inst Geol, Ciudad Univ, Coyoacan 04510, Cdmx, Mexico
Griffin, William L.:
Macquaric Univ, ARC Ctr Excellence Core Crust Fluid Syst CCFS, Dept Earth & Planetary Sci, Sydney, NSW 2109, Australia
Macquaric Univ, GEMOC Natl Key Ctr, Dept Earth & Planetary Sci, Sydney, NSW 2109, Australia
Gervilla, Fernando:
Univ Granada, Dept Min & Petrol, Fac Ciencias, Ave Fuentenueva S-N, Granada 18002, Spain
Univ Granada CSIC, Inst Andaluz Ciencias Tierra, Ave las Palmeras 4, Granada 18100, Spain
O'Reilly, Suzanne Y.:
Macquaric Univ, ARC Ctr Excellence Core Crust Fluid Syst CCFS, Dept Earth & Planetary Sci, Sydney, NSW 2109, Australia
Macquaric Univ, GEMOC Natl Key Ctr, Dept Earth & Planetary Sci, Sydney, NSW 2109, Australia
Escayola, Monica F.:
Univ Tierra del Fuego, Ist Ciencias Polares & Ambientales ICPA, CONICET, Fueguia Basket 251, RA-9410 Ushuaia, Tierra Del Fueg, Argentina
All Open Access, Gold
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