Discovery of a dismembered metamorphic sole in the Saga ophiolitic mélange, South Tibet: Assessing an Early Cretaceous disruption of the Neo-Tethyan supra-subduction zone and consequences on basin closing

A Petrographic Atlas of Ophiolite

“…They contain variable amounts of quartz, alkali feldspar, plagioclase, amphibole, and minor biotite, muscovite, epidote, pyrite, chalcopyrite and magnetite as accessories. Similar temperatures were also estimated in the Indus-Tsangpo suture ophiolites including metamorphic sole of the Saga ophiolitic mélange (850°C at 1.2 GPa, Guilmette et al 2012) and the peridotites associated with the Spontang (1000-1200°C, Reuber 1986) and the Yungbwa (900-960°C, Miller et al 2003) ophiolites. The plagioclase shows alteration to sassurite.…”

Dynamics of intraoceanic subduction initiation: 2. Suprasubduction zone ophiolite formation and metamorphic sole exhumation in context of absolute plate motions

“…Metamorphic soles thus start forming at depths up to 45 km below a hot mantle, and subsequently grow by accretion to their base during decompression and cooling to even nonmetamorphic conditions, while maintaining a widespread coverage below the fore arc, up to 100 km or more away from the trench. 40 Ar/ 39 Ar amphibole cooling ages for the sole typically overlap with or are a few million years younger than crustal crystallization ages of the overlying SSZ ophiolites [Hacker, 1994;Hacker et al, 1996;Wakabayashi and Dilek, 2000;Dimo-Lahitte et al, 2001;Çelik et al, 2006;Guilmette et al, 2009Guilmette et al, , 2012H ebert et al, 2012;Rioux et al 2012Rioux et al , 2013So starić et al, 2014]. Exhumation and cooling of metamorphic soles thus likely starts during the spreading that ultradepletes the mantle wedge and produces the ophiolitic SSZ crust above the sole, and continues a few million years beyond the magmatic spreading stage when exhumation and cooling of the sole occurs at temperatures much lower than those that allow mantle melting.…”

“…Metamorphic soles thus start forming at depths up to ∼45 km below a hot mantle, and subsequently grow by accretion to their base during decompression and cooling to even nonmetamorphic conditions, while maintaining a widespread coverage below the fore arc, up to 100 km or more away from the trench. 40 Ar/ 39 Ar amphibole cooling ages for the sole typically overlap with or are a few million years younger than crustal crystallization ages of the overlying SSZ ophiolites [ Hacker , ; Hacker et al ., ; Wakabayashi and Dilek , ; Dimo‐Lahitte et al ., ; Çelik et al ., ; Guilmette et al ., ; Hébert et al ., ; Rioux et al . ; Šoštarić et al ., ].…”

OIB- and P-type ophiolites along the Yarlung- Zangbo Suture Zone (YZSZ), Southern Tibet: Poly- Phase melt history and mantle sources of the Neotethyan oceanic lithosphere

“…2). The mélange contains blocks of lherzolitic, dunitic peridotites and garnet-and cpxbearing amphibolites in a serpentinite matrix (Bédard et al, 2009;Guilmette et al, 2012). Structurally below this mélange in the south is a 2-to 2.5-km-thick unit of meta-gabbro, amphibolite and metabasaltic rocks that is in turn tectonically underlain by a ~2-km-thick sequence of pillow to massive lavas, diabasic rocks, and Triassic green-red chert.…”