Upper Tertiary and Quaternary volcanism and subduction zone regression, North Island, New Zealand

The Coromandel Peninsula comprises the central subaerial part of the late Cenozoic Coromandel Volcanic Zone (CVZ) of New Zealand and hosts the Hauraki Goldfield. Some 73 K-Ar and 9 zircon fission-track dates representative of 28 lithostratigraphic volcanic units mapped on the peninsula are reported, and more than 250 major element analyses of volcanic rocks, including all the dated rocks, have been collated and their broad geochemical affinities used to underpin the stratigraphy and volcanic history of the region.The age data confirm that the central part of the CVZ evolved more or less continuously throughout the late Cenozoic from c. 18 to 4 Ma ago (late-early Miocene to early Pliocene), with regional time breaks of no more than i -2 Ma. From c. 18 to 9 Ma, an andesite-dominated volcanic arc was active, and at c. 10 Ma initiation of the Kapowai Caldera began with the first eruption of ignimbrite. A bimodal basalt to basaltic andesite/rhyolite association developed from c. 9 to 7 Ma and accompanied major caldera collapse, ignimbrite eruption, and postcaldera andesite eruption. Bimodal eruptions of basalt to basaltic andesite (with minor andesite) plus rhyolite and rhyolitic ignimbrite began once more from c. 6 to 5.5 Ma, and these became entirely basaltic from 4.7 to 4.2 Ma. At about the same time (c. 5.5 Ma), basalt was also erupted on the southern Colville Ridge. During late Miocene to early Pliocene time, andesitic to dacitic eruptions continued in the south and southwest of the CVZ. With time, the locus of volcanism moved irregularly eastwards at c. 3 mm/yr and southwards at c. 8 mm/yr, such that minimum ages are younger progressively southwards.Volcanism in the Coromandel Peninsula is mainly calcalkaline and medium-K, with some early and late lavas showing tholeiitic affinities. The rocks range from highalumina basalts (including picritic basalt) through basaltic andesites and (dominant) andesites to dacites. There is an apparent gap between dacites at 63-68% SiO 2 and rhyolites/ ignimbrites at 73-78% SiO 2 , several of which have high-K affinities. Many of the volcanic formations have distinct chemical signatures, confirming earlier suggestions that each has an independent magmatic history.

Section: Overall Age Trendsmentioning

confidence: 99%

Section: Whitianga Group Coroglen Subgroup Carina Rock Ignimbritementioning

confidence: 99%

Geochronological and geochemical evolution of late Cenozoic volcanism in the Coromandel Peninsula, New Zealand

Adams¹,

Graham²,

Seward³

et al. 1994

“…The southwest-dipping trench-arc system was initially established in Northland. However, the history of its progression to the present position is still being debated (Kamp 1984;Brothers 1986;Ballance 1988;Kear 1994). Synchronous with this development was the formation of the Alpine Fault as a continuous transform through the New Zealand block, intersecting obliquely the earlier late Eocene to mid Oligocene rift system of western South Island (Kamp 1986b).…”

Section: Introductionmentioning

confidence: 99%

Thermal history of the early Miocene Waitemata Basin and adjacent Waipapa Group, North Island, New Zealand

Raza

Brown

Ballance

et al. 1999

Apatite fission track (AFT) and vitrinite reflectance (VR) data for early Miocene outcrops from the Waitemata Basin reveal that the basin sequence was subjected to shallow burial before denudation. AFT results suggest that the total sediment thickness within the basin was 1 km and maximum paleotemperatures during burial never exceeded c. 60°C. Statistical analyses of the detrital AFT ages distinguish four dominant sources of sediment supply: contemporaneous volcanism; metagreywacke rocks of the Waipapa Group; the Northland Allochthon; and an unidentified source south of the basin.The apatite and zircon fission track results from the Waipapa Group rocks (Gondwana Terrane) adjacent to the basin suggest two discrete phases of accelerated cooling: the first during the early Cretaceous (c. 117 Ma) and the second during the mid Cretaceous (c. 84 Ma). These events probably reflect key stages in the tectonic development of the New Zealand microcontinent during the Cretaceous period, the earlier event being related to the climax of compressional deformation (Rangitata Orogeny) and the latter to extensional tectonism associated with the opening of the Tasman Sea. Waipapa Group rocks now exposed at the surface cooled from maximum paleotemperatures of c. 250°C at an estimated rate of c. 180-36°C/m.y., involving substantial denudation.

“…Thompson (1965), Brothers (1986), and Smith et al (1989) have contrasted the late Cenozoic volcanics of eastern Northland with those of western Northland. Their eastern Northland belt of calc-alkaline andesites (aged 22-16 Ma, Smith et al 1986) extended southwards from North Cape, through Whangarei, towards Coromandel.…”

Section: Coromandel and Great Barrier Islandmentioning

confidence: 99%

“…Smith et al (1989) noted the two belts in Northland, but did not believe that the western belt was represented south of Manukau Heads. Brothers (1984Brothers ( , 1986 identified the two belts in Northland, and followed Challis (1978) in showing "timelines" from 21 Ma ago, indicating what he called subduction zone regression towards a trough at broadly the present site of the Hikurangi Trough. Ballance (1988) disputed that view.…”

Section: Introductionmentioning

confidence: 99%

A “least complex” dynamic model for late Cenozoic volcanism in the North Island, New Zealand

Karátson

1994