Zircon Hf isotope signature of the depleted mantle in the Myanmar jadeitite: Implications for Mesozoic intra-oceanic subduction between the Eastern Indian Plate and the Burmese Platelet

A revisit to the Yorii jadeite–quartz rock, the Kanto Mountains, central Japan: Implications for petrogenesis

“…It generally occurs as blocks, in association with high-pres sure/low-temperature rocks, within serpentinite (cf., Tsujimori and Harlow, 2012). Its genesis has attracted much attention recently (Tsujimori et al, 2005;Bröcker and Keasling, 2006;Shi et al, 2008Shi et al, , 2009Qiu et al, 2009;Fu et al, 2010Fu et al, , 2012Yui et al, 2010Yui et al, , 2012Yui et al, , 2013Meng et al, 2011;Mori et al, 2011;Cárdenas-Párraga et al, 2012;Schertl et al, 2012;Flores et al, 2013;Fukuyama et al, 2013). Two formation mechanisms have been proposed: the wholesale metasomatic replacement and the vein precipitation (Harlow et al, 2007(Harlow et al, , 2014(Harlow et al, , 2015Yui et al, 2010;Tsujimori and Harlow, 2012).…”

Spherules with pure iron cores from Myanmar jadeitite: Type-I deep-sea spherules?

“…Albitite is petrogenetically closely related to jadeitite, however, the origin of albitite in subduction zones is even more poorly understood than that of jadeitite. Combined with findings of a low-salinity, seawater-like fluid in jadeitite (Johnson and Harlow, 1999;Shi et al, 2005b), the finding of type-I like spherules in the Myanmar jadeitite allow us to suggest that the jadeitite-forming materials were derived from, or at least partially from oceanic sediments on subducted altered oceanic crust, coupled with dehydration of the sediments and the altered oceanic crust (e.g., Shi et al, 2009a;Simons et al, 2010;Harlow et al, in press).…”

“…Methane (CH 4 ) bearing fluid inclusions found in jadeites from the Myanmar jadeitite confirm a fluid-related origin and suggest a reduced environment (Shi et al, 2005b;Sorensen et al, 2006). Studies on zircons in jadeitite from Myanmar and elsewhere suggest that their derivation can be from rapid reworking of juvenile oceanic crust, which was hydrated during its formation as revealed from highly positive depleted-mantle eHf (t) values (Qiu et al, 2008;Shi et al, 2009a), although aqueous solutions possibly related to serpentinization are suggested by low Th/U and fluid inclusions (Yui et al, 2010), and zircons in jadeitite can have multiple origins (Fu et al, 2010).…”

“…Because the Myanmar jadeitites have been considered to form from fluids related to dehydration of seawater-altered oceanic crust or serpentine minerals under high pressure and low temperatures in a subduction zone (Harlow, 1994;Essene and Fyfe, 1967;Shi et al, 2005bShi et al, , 2009aSorensen et al, 2006;Harlow et al, 2007), the spherules from the jadeitite are likely to have experienced a series of events including: entry through the atmosphere, landing on seafloor, transport with the oceanic slab into a subduction zone, high P/T metasomatism/metamorphism along with entrapment by jadeitite, and ultimate exhumation. These processes can be traced back to Late Jurassic when the jadeitite formed (Shi et al, 2008).…”

“…Jadeitite, a rock made up almost entirely of jadeitic pyroxene, always occurs in serpentinites, and is associated with eclogite or blueschist within subduction zones (Harlow, 1994;Harlow et al, 2007;Shi et al, 2008Shi et al, , 2009aGarcia-Casco et al, 2009). Though jadeitite is found in only about 15 locations worldwide (e.g., Coleman, 1961;Essene and Fyfe, 1967;Bender, 1983;Harlow et al, 2007), its petrogenesis represents an important geological process, which can give us a better understanding of jadeitites and associated rocks, of their relationship to eclogites and/or blueschists, and host serpentinized peridotite, of fluids that form jadeitites, and possibly of sodium metasomatism during subduction processes.…”