Petrology and geochemistry of chromian spinel-bearing serpentinites in the Hida Marginal Belt (Ise area, Japan): characteristics of their protoliths

Abstract

The Ise area is located in the western part of the Hida Marginal Belt (central Japan), which includes several sporadic exposures of ultramafic rocks, sometimes forming a serpentinite mélange of the Paleozoic age. Ultramafic rocks in the Ise area, enveloped by Paleozoic -Mesozoic sedimentary rocks, are completely serpentinized; however, the abundance of bastite after orthopyroxene suggests harzburgite protoliths. ) atomic ratio, <0.03]}, similar to chromian spinel in Kotaki and Oeyama ultramafic masses. It is also similar in chemistry to spinels in forearc and abyssal peridotites, suggesting two possibilities for the derivation of the Ise serpentinite's protoliths. The degree of melting using Cr# versus TiO 2 of chromian spinel is ~ 20 -25%, which is in accordance with the harzburgite protoliths obtained by whole -rock chemistry models. We found that Cr, Al, Ni and Ca, preserved in bastite and meshtextured serpentine, are conservative during serpentinization, confirmed from the similarity in the whole -rock A1 and Ca of the Ise serpentinites to Horoman harzburgites. The occurrence of dolomite can stabilize the Ca and limited its mobility to escape outside the serpentinites. The harzburgite protoliths were possibly serpentinized by slab -derived fluids at a shallow depth relative to the Happo -O'ne serpentinites during the exhumation process.

Spinel chemistry and geochemistry of serpentinite of North Delhi fold belt, Rajasthan: Constraining the petrogenesis and geodynamics of northwestern Indian shield

“…Conversely, the abyssal peridotite that is, a portion of upper mantle exposed in mid‐ocean ridge setting, subsequently get emplaced in a forearc setting without exhibiting any evidence for their participation in partial melting in the mantle wedge (Batanova & Sobolev, 2000; Parkinson & Pearce, 1998; Parkinson, Pearce, Thirlwall, Johnson, & Ingram, 1992; Pearce, Barker, Edwards, Parkinson, & Leat, 2000; Uysal et al, 2012, 2014). Here, the chemistry of unaltered Cr‐spinel is used to discriminate between different tectonic settings for the studied serpentinite (e.g., Arai, 1992, 1994; Arai et al, 2011; Barnes & Roeder, 2001; Dick & Bullen, 1984; Kamenetsky et al, 2001; Khedr & Arai, 2011, 2013, 2016; Zhou & Robinson, 1997). High Cr# (>0.6) is usually restricted to the subduction‐related rocks (e.g., Arai, 1994; Arai et al, 2011; Dick & Bullen, 1984; Ishii, Robinson, Maekawa, & Fiske, 1992; Khedr & Arai, 2011), whereas Cr# (<0.6) refers to abyssal or mid‐ocean ridge (MOR) peridotites (e.g., Arai, 1994; Barnes & Roeder, 2001; Dick & Bullen, 1984; Ishii et al, 1992).…”

“…Here, the chemistry of unaltered Cr-spinel is used to discriminate between different tectonic settings for the studied serpentinite (e.g., Arai, 1992Arai, , 1994Arai et al, 2011;Barnes & Roeder, 2001;Dick & Bullen, 1984;Kamenetsky et al, 2001;Khedr & Arai, 2011Zhou & Robinson, 1997). High Cr# (>0.6) is usually restricted to the subduction-related rocks (e.g., Arai, 1994;Arai et al, 2011;Dick & Bullen, 1984;Ishii, Robinson, Maekawa, & Fiske, 1992;Khedr & Arai, 2011), whereas Cr# (<0.6) refers to abyssal or mid-ocean ridge (MOR) peridotites (e.g., Arai, 1994;Barnes & Roeder, 2001;Dick & Bullen, 1984;Ishii et al, 1992). Considering the range of Cr# from 0.55 to 0.62 with a dominant cluster of little less of 0.6 (average 0.58), the studied samples show a mid-ocean ridge-arc transition setting (Salters & Stracke, 2004;Figure 7a), which is also reflected in TiO 2 versus MgO (wt%) bivariate diagram (Figure 7b).…”

Petrogenetic Significance of Spinels From Serpentinised Peridotites From the Verianaousa Ophiolite

“…Furthermore, the formation of ferrian-chromite and chromian magnetite alteration rims around the Al-spinels, Cr-spinels and magnesiochromites is assigned to secondary processes that typically occur during serpentinisation (Khedr and Arai, 2011;Singh et al, 2013;Banerjee et al, 2015;Maulana et al, 2015). Notable Mn-erichments in the ferrian chromite zones involve interaction of hydrothermal fluids that were likely rich in Mn, similarly to other ophiolite complexes (e.g., Gahlan and Arai, 2007).…”

Υπολείμματα Ανώτερου Μανδύα Και Ωκεάνιου Φλοιού Από Περιοχές Της Κεντρικής Μακεδονίας

“…γρανοφυρικού ιστού σε ορθόκλαστο (or) (ΒΕ.20, Nicols +), δ) Φωτομικρογραφία φλέβας επίδοτου (ep) και χλωρίτη (chl) που διαπερνά δείγμα γρανίτη (ΒΕ.20, Nicols +), ε) Μικροφωτογραφία (BSE) υπιδιόμορφου κρυστάλλου χλωρίτη (chl) σε δείγμα γρανοδιορίτη στην ορυκτολογική σύσταση του οποίου συμμετέχουν πλαγιόκλαστα (plg), χαλαζίας (qz) και τιτανίτης (ttn) (BE.138), στ) παρουσιάζουν γενικά χαμηλά ποσοστά σε Al2O3, Cr2O3 και TiO2. Οι πορφυροκλάστες εμφανίζουν χαμηλότερες τιμές σε Ca και Fe, αλλά υψηλότερες τιμές σε Al, Cr, Εικόνα 4.10(Michailidis 1990, Burkhard 1993, Barnes 2000, Khedr & Arai 2011, Banerjee et al 2015, Maulana et al 2015 είτε σε μεταμορφικές διεργασίες μεταγενέστερες της σερπεντινίωσης(Mellini et al 2005, Merlini at al. 2009) ή προγενέστερες της σερπεντινίωσης(Kapsiotis 2015) είτε σε μεταγενέστερη μαγματική εξαλλοίωση(Economou- Eliopoulos 2003, Mukherjee et al 2010, Arai & Akizawa 2014.…”