Jarbo Gap ophiolite
Jarbo Gap ophiolite
Early Jurassic and Late Triassic, ~196-204 Ma
Ophiolitic mélange. Tectonized ultramafic, metagabbro, amphibolite, metavolcanic, and metasedimentary rocks. Serpentinite is commonly schistose but also includes serpentinized harzburgite and dunite with chromite-rich layers. Serpentinite and metagabbro intruded by multiple generations of mafic to felsic dikes; dikes folded. Subsequently overlain by mafic breccia, then intruded by plagiogranite and randomly oriented mafic dikes. A plagiogranite dike has yielded an age of ~196 Ma (Dilek, 1989). Metasedimentary rocks include phyllite and metachert. Metagabbro locally strongly foliated. Equivalent in part to ophiolite mélange member of Fiddle Creek complex of Edelman and others (1989), but that designation is herein abandoned because the chert-argillite member of the Fiddle Creek complex includes relatively unmetamorphosed rocks of the same age.