A shallow origin for diamonds in ophiolitic chromitites
Por:
Farre-de-Pablo, Julia, Proenza, Joaquin A., Maria Gonzalez-Jimenez, Jose, Garcia-Casco, Antonio, Colas, Vanessa, Roque-Rossell, Josep, Camprubi, Antoni, Sanchez-Navas, Antonio
Publicada:
1 ene 2019
Categoría:
Geology
Resumen:
Recent findings of diamonds in ophiolitic peridotites and chromitites
challenge our traditional notion of Earth mantle dynamics. Models
attempting to explain these findings involve incorporation of diamonds
into chromite near the mantle transition zone. However, the occurrence
of metastable diamonds in this context has not been considered. Here, we
report for the first time in situ microdiamonds in chromite from
ophiolitic chromitite pods hosted in the Tehuitzingo serpentinite
(southern Mexico). Here, diamonds occur as fracture-filling inclusions
along with quartz, clinochlore, serpentine, and amorphous carbon, thus
indicating a secondary origin during the shallow hydration of
chromitite. Chromite chemical variations across the diamond-bearing
healed fractures indicate formation during the retrograde evolution of
chromitite at temperatures between 670 degrees C and 515 degrees C.
During this stage, diamond precipitated metastably at low pressure from
reduced C-O-H fluids that infiltrated from the host peridotite at the
onset of serpentinization processes. Diamond was preserved as a result
of fracture healing at the same temperature interval in which the
chromite alteration began. These mechanisms of diamond formation
challenge the idea that the occurrence of diamond in ophiolitic rocks
constitutes an unequivocal indicator of ultrahigh-pressure conditions.
Filiaciones:
Farre-de-Pablo, Julia:
Univ Barcelona, Dept Mineral Petrol & Appl Geol, Marti i Franques S-N, E-08028 Barcelona, Spain
Proenza, Joaquin A.:
Univ Barcelona, Dept Mineral Petrol & Appl Geol, Marti i Franques S-N, E-08028 Barcelona, Spain
Maria Gonzalez-Jimenez, Jose:
Univ Granada, Fac Sci, Dept Mineral & Petrol, Ave Fuentenueva S-N, Granada 18002, Spain
Garcia-Casco, Antonio:
Univ Granada, Fac Sci, Dept Mineral & Petrol, Ave Fuentenueva S-N, Granada 18002, Spain
Univ Granada, CSIC, Spanish Res Council, Andalusian Earth Sci Inst IACT, Ave Palmeras 4, Granada 18100, Spain
Colas, Vanessa:
Univ Nacl Autonoma Mexico, Inst Geol, Ciudad Univ, Mexico City 04510, DF, Mexico
Roque-Rossell, Josep:
Univ Barcelona, Dept Mineral Petrol & Appl Geol, Marti i Franques S-N, E-08028 Barcelona, Spain
Camprubi, Antoni:
Univ Nacl Autonoma Mexico, Inst Geol, Ciudad Univ, Mexico City 04510, DF, Mexico
Sanchez-Navas, Antonio:
Univ Granada, Fac Sci, Dept Mineral & Petrol, Ave Fuentenueva S-N, Granada 18002, Spain
Univ Granada, CSIC, Spanish Res Council, Andalusian Earth Sci Inst IACT, Ave Palmeras 4, Granada 18100, Spain
|