Saga ophiolite from the mid-western part of the Yarlung-Zangbo ophiolite belt was researched in this paper. The data of petrogeochemistry

geochronology

chronology

geotectonics and geodynamics indicate that gabbro in Saga ophiolite was originated from calc-alkaline low-potassium tholeiitic basalt. The basalt in Saga ophiolite is calc-alkaline and alkali. The basalts in Rega and Songduo section line are calc-alkaline low-potassium tholeiitic basalts. The basite in Saga ophiolite has the same geochemical characteristics as MORB

tholeiitic and alkaline basalt. In summary

the Saga ophiolite in the northern sub-belt was originated from various multiple resources. It is generally depleted in Cr

Ti

Mn. The geochemical characteristics of trace elements are similar to mantle. A large area of alkaline basalt was found in the saga ophiolite

retaining geochemical characteristics of mantle with enriching alkali. Zircon U-Pb age of the gabbro in Dajiling-Sala profile is 125.6±2.7 Ma

in accordance with the basaltic age (130 to 120 Ma) in western Yarlung-Zangbo ophiolite. It is inferred that the Saga ophiolite is possible to form in the intra-oceanic supra-subduction zone (SSZ)

suffering from expansion in mid-oceanic ridge situated in the forearc basin.