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64 OPHIOI ITES AND VOl CANle ROCKS IN mE HUMBER ARM ANp HARE
BAy AllOCHTHONS
Within the both the Hare Bay and Humber Arm Allochthons ophiolitic rocks
~onstitule the highest 5lructural slices. In the Humber Arm Allochthon. the Bay of
Islands Complex (BOle) has long been considered a classic example of the completc
ophiolite suite, whereas in the Hare Bay Allochthon, only the lower ultramafic pallS of
the ophiolite are preserved as the White Hills Pcridolite. Lithologies within the BOle
include harzburgilc. lherzolite. gabbro. trondhjemiteS and basal!. ChemicaJly, the
volcanjcs vary from bullts to basahic andesites (knntr CI al. 1991). Previow.ly. the
BOIC was moughllO lu.vc been formed al a mid«ean ridge. but has now betn re·
inlerpreu~d as having been formed in a back-arc twin (Jenner ct aI .. 1991).
Another highslice wilhin the Humber Arm Allochthon is the Linle Pon Comptex.
Dunning CI al. (1991) describe the lillIe Pon Complell as 'a suucturally complell
assemblage of mafrc and felsic volcanic rocks and trondhjemite comprising the highesl
and mOSI weslerly structural unit oflhe Bay of Islands area. Rean! detailed geochemical
studies (Jenner el aI., unpu:..rished data) suongly indicate an island arc origin for the
complell.
Felsic volcanics in the complell are gtoehemicalJy similar to the dated
trondjhemite, suggcsling contemporaneity of volcanism and plutonism. Spatially
associated mafic lavas are island arc tholeiites'. The linle Port Complex Iw been