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Eclogite of high-pressure low-temperature origin occurs within the Great Serpentine belt of New South Wales. The presence of glaucophane-bearing rocks and other medium to high-pressure assemblages associated with the belt is similar in many respects to the Californian and Oregon occurrences. The chemical composition of the eclogite is characterized by low K2O values comparable to many oceanic tholeiites, although one analysis is nepheline-normative. Ti-Zr-Y ratios also show affinities to ocean-floor basalts.The garnet contains approximately 30% grossular and is strongly zoned from almandine (Alm 56%, Py 9%) at the core towards pyrope (Alm 44%, Py 27%) at the margin. Sodic augite contains 30-33% Jd, 4-7% Ac, and 72-74% Di+He.Distribution of Fe and Mg between co-existing garnet and pyroxene would suggest an increasing temperature during eclogite crystallization with a possible range from 290°C to 600°C and a minimum pressure of 7-12 kb.

New data for the Wologorong Batholith, northwest of Goulburn, New South Wales, indicate that it is S-type and probably similar in age to the major batholith in the southern part of the Lachlan Fold Belt. Its component rocks are predominantly biotite and biotite-muscovite adamellite, and have a strong N-S metamorphic foliation. An isochron, defined by fourteen rocks, gives a Rb/Sr age of 405 ±11 Ma and an initial 87Sr/86Sr ratio of 0.7110 ± 0.0012. Five Rb/Sr biotite ages range between 339 and 381 Ma, the older ages being obtained from the least deformed parts of the Batholith. Whereas uncertainties inherent in dating a deformed S-type batholith make 405 Ma a reconnaissance value only, the minimum emplacement age for the Batholith, as determined from two biotites, is around 381 Ma. The younger biotite ages, around 339 to 348 Ma, are considered to date a major period of regional metamorphism in the northeastern part of the Lachlan Fold Belt, similar to that recorded from K/Ar ages of metamorphic biotite in the Hill End region 100 km to the north.The I-S line of Siluro-Devonian granites, defined in the southern part of the Lachlan Fold Belt, extends in a NNE direction, and passes to the east of the Wologorong Batholith. To the north of the Carboniferous Bathurst, the position of the line is uncertain, because of the absence of Siluro-Devonian S-type granites, and establishing its presence may depend on the nature of the volcanic rocks, as yet not investigated.

Woodlark Island, the largest above-sea portion of the Woodlark Rise, has an exposed basement of pre-Miocene (?Cretaceous-Eocene) low-K tholeiitic basalt and dolerite, and minor sediments. The basement is unconformably overlain by Early Miocene limestone and volcaniclastic sediments and later Miocene high-K volcanics and comagmatic intrusives. Pleistocene to Recent sediments partly blanket the Tertiary sequence. Basement low-K tholeiites vary only slightly in composition and are interpreted as ocean floor or possible marginal basin material. The high-K suite appears to be chemically similar to late Tertiary to Recent high-K igneous rocks of mainland Papua New Guinea. It includes porphyritic hornblende-, clinopyroxene-, biotite- and magnetite-bearing shoshonite, latite and toscanite, and intrusive equivalents that range from olivine normative to strongly quartz normative compositions (S1Q2 46% to 75%). Computer mixing models indicate that separation of the pheno-crysts in the shoshonites, particularly pargasitic hornblende, is a feasible mechanism for producing the more silica-rich monzonites and latites.The low-K tholeiitic basement rocks of Woodlark Island are inferred to be part of an ophiolitic slab en echelon with the Papuan Ultramafic Belt, thrust over equivalents of the Cretaceous Owen Stanley Metamorphics or, in part, onto existing oceanic crust. High-K igneous rocks on Woodlark Island appear to form an eastward extension of a province of calcalkaline to shoshonitic volcanic and intrusive rocks, which stretches from Mount Lamington to the Louisiade Archipelago. Late-middle Miocene high-K magmatism at Woodlark Island is consistent with the observation that activity commenced earlier in the E and became progressively younger westwards towards mainland Papua New Guinea. Periodicity in the magmatism was apparently synchronous with major rifting episodes that formed the Woodlark Basin. The data on the Woodlark Island high-K suite support the currently accepted. concept of delayed partial melting of a mantle source previously modified by the introduction of water and LILE from an earlier subduction zone (Johnson et al., 1978b).

Ultramafic hornfelses containing the assemblages hornblende + olivine + spinel + magnetite, and clinopyroxene + olivine + spinel + magnetite, are reported from two localities in the Biggenden Beds in southeastern Queensland. They are associated with mafic hornfelses in the contact metamorphic aureoles of the Mungore Adamellite and the Wateranga Gabbro. Chemical composition and minerology of the olivine + amphibole + spinel + magnetite hornfelses suggest that they represent metamorphosed picritic rocks, or possibly, altered serpentinites (blackwall rocks), whereas the clinopyroxene + olivine + spinel + magnetite hornfelses are interpreted as metamorphosed altered clinopyroxene-rich picritic rocks. Cr-Fe spinel relations in the hornfelses indicate partial homogenisation of primary chromian spinel with secondary magnetite ± ferrichromite during contact metamorphism.

The Ben Bullen plutons constitute a small medium-K gabbro-tonalite-trondhjemite suite spatially and temporally associated with extensive adamellite and granite of the Bathurst Batholith. The mafic composition of the bulk of the Ben Bullen rocks suggests a mantles source for the parent magma. Chemical and petrographic studies indicate that the rocks are closely comparable with medium-K calc-alkaline volcanic suites in island arcs. The Ben Bullen series are M-type granites in the sense of being formed by crystal fractionation of a gabbroic parental magma. Initial crystallization and separation of olivine and pyroxene followed by marked fractionation of hornblende probably drove the differentiating magma along a typical calc-alkaline trend of strong alkali-enrichment. It is possible that the rise of these mantle-derived melts into the crust initiated the crustal melting that produced the associated felsic K-rich granitoids of the Bathurst Batholith.