Lamprophyre dike intrusion and the age of the Alpine fault, New Zealand

Cooper, Alan F.; Barreiro, B. A.; Kimbrough, David L.; Mattinson, James M.

doi:10.1130/0091-7613(1987)15<941:ldiata>2.0.co;2

Cited by 187 publications

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“…Spreading continued until about 30 Ma (Oligocene), when a small amount of relative motion that had developed between the Pacific and Australian plates became more oblique [Wood and Sutherland, 1997]. The Alpine fault, the surface trace of the Pacific-Australian plate boundary through southern New Zealand, developed as a through-going strike-slip plate boundary at about 25 Ma [Molnar et al, 1975;Carter and Norris, 1976; Cooper et al, 1987]. A change in the relative plate motion along the Pacific-Indian plate boundary ---10 Myr ago [Molnar et al, 1975;Carter and Norris, 1976] resulted in increasingly oblique motion on the Alpine fault.…”

Section: Davey Et Al 1998mentioning

confidence: 99%

Crustal structure and thermal anomalies of the Dunedin Region, South Island, New Zealand

Godfrey¹,

Davey²,

Stern³

et al. 2001

J. Geophys. Res.

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Abstract. Seven geophysical data sets are used to investigate a transect along the southeast coast of South Island, New Zealand. The specific focus of this study is the Dunedin volcanic center, which last produced volcanics at the surface 13-10 Myr ago. Wide-angle reflection/refraction seismic data along a two-dimensional profile reveal a lowvelocity lower crust and mantle beneath the Dunedin volcanic center. The low-velocity lower crust coincides with a highly reflective region on a nearby multichannel seismic line and may represent a hot, fluid-rich region of the crust. In addition, high mantle helium ratios measured in the Dunedin region suggest a current or recent mantle-melting event. High heat flow recorded in the Dunedin region is consistent with a hot body emplaced in the midcrust --•10 Myr ago (Miocene) whose heat is just reaching the surface today. Uplift of an Oligocene limestone horizon in the Canterbury basin can be explained by a buoyant load beneath the Dunedin volcanic center and low flexural rigidity of the lithosphere beneath the volcanic center during the Miocene. We interpret the data as revealing two separate thermal events beneath the Dunedin volcanic center, one during the Miocene, when volcanism was last occurring at the surface, and the other occurring currently. Active volcanism associated with the current mantle-melting event has yet to reach the surface. Geophysical Data and ModelsData used to develop and constrain models presented here are WAR/R seismic data, MCS data from industry and the SIGHT program, petrophysical measurements, and helium isotope and heat flow data. -1000 '• -, , , , , -, , , , , Figures 3a and 3b). On gather OBH 27, however, the Pn phase, which also passes through relatively fast lower crust (6.5-6.7 km s-•), can be flattened using an apparent velocity of---8.1 km s -• (Figure 3c Figures 5a and 5c) [Holt and Stem, 1994]. As SIGHT lines 4E and 25E approach Dunedin, this reflector is uplifted, and on SIGHT line 25E it is truncated at the surface (Figure 5c). It was presumably deposited horizontally, which makes it a useful marker horizon whose profile can be used to calibrate uplift. The age of uplift can be estimated from the age of the shallowest uplifted horizon on which there are onlapping sediments as seen on SIGHT line 4E (Figure 5a). Industry Well DataTwo industry wells either on, or close to, three of the SIGHT MCS lines (Figure lc) are used to date the horizon that we expect to be the Oligocene limestone and the shallowest uplifted horizon. We mapped both horizons from SIGHT line 4E to SIGHT lines 2E and 25E (Figure 5). On SIGHT lines 25E and 2E the deeper prominent reflector ties with the Oligocene limestone horizon in the well logs of the Galleon-1 well (Figures lc and 5c (Figures 5b and 5c).

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Section: Davey Et Al 1998mentioning

confidence: 99%

Crustal structure and thermal anomalies of the Dunedin Region, South Island, New Zealand

Godfrey¹,

Davey²,

Stern³

et al. 2001

J. Geophys. Res.

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“…Combined with the biotite K/Ar cooling ages of 44-61 Ma (Rattenbury 1987) this would constrain the ductile mylonitization that affected the trachyte dike to have occurred between an interval with 72 and 44 Ma as the oldest and youngest possible ages, respectively. However, this age range precedes the onset of the Alpine Fault at 30-25 Ma (Cooper et al 1987;Schellart et al 2006;Furlong & Kamp 2009). Therefore, the ages in the Fraser Complex would imply that a previously unidentified stage of deformation between 72 and 44 Ma is recorded within the Fraser Complex that has no equivalent elsewhere in the Western Province.…”

Section: Deformation and Magmatism In The Fraser Complexmentioning

confidence: 99%

Magmatism during Gondwana break-up: new geochronological data from Westland, New Zealand

Meer

Scott

Waight

et al. 2013

New Zealand Journal of Geology and Geophysics

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Newly determined Late Cretaceous 40 Ar/ 39 Ar ages on megacrystic kaersutite from four lamprophyre dikes, and a U-Pb zircon age on a trachyte, from central and north Westland (New Zealand) are presented. These ages suggest that the intrusion of mafic dikes (88-86 and 69 Ma) was not necessarily restricted to the previously established narrow age range of 80-92 Ma. The younger lamprophyre and trachyte dikes (c. 68-70 Ma) imply that tensional stresses in the Western Province were either renewed at this time, or that extension and related magmatism continued during opening of the Tasman Sea. Extension-related magmatism in the region not only preceded Tasman seafloor spreading initiation (starting at c. 83 Ma, lasting to c. 53 Ma), but may have sporadically continued for up to 15 Ma after continental break-up.

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“…The transcurrent plate boundary through New Zealand was initiated in the Miocene, and this resulted in a change back to compressional deformation in the Otago Schist belt (Cooper et al 1987). Many parts of the rectilinear pattern of normal faults were reactivated as reverse faults.…”

Section: Post-metamorphic Deformationmentioning

confidence: 99%

Structural and lithological controls on gold mineralisation at Oturehua on the northeastern margin of the Otago Schist, New Zealand

Mackie

MacKenzie

Craw³

2009

New Zealand Journal of Geology and Geophysics

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A set of more than 50 mineralised normal faults cuts lower greenschist facies rocks at the northeastern margin of the Otago Schist belt near Oturehua, central Otago. The faults strike northwest and dip steeply (>60°) northeast, and individual mineralised zones are traceable for up to 700 m along strike. The mineralised faults are closely associated with, and are generally parallel to, a swarm of northwest striking, steeply dipping extensional quartz ± ankerite veins (centimetre scale) that occur over an area of at least 25 km 2 in the host schist. Mineralised faults contain 10-100 cm thick quartz veins that are traceable as interlinked structures for tens of metres along strike. where faults cut massive quartz-feldspar-rich schist, the veins are planar, contain scattered sulfide minerals and visible gold, and there has been little alteration of essentially undeformed adjacent wall rock (centimetre scale). in contrast, muscovite-rich laminated schist host rock is extensively deformed and altered adjacent to mineralised faults (metre scale), with addition of quartz (silicification) and ankeritic replacement of metamorphic chlorite by kaolinite and/or sericitic muscovite. Veins adjacent to laminated (micaceous) schist contain abundant breccias with variably altered clasts. widespread addition of auriferous sulfide minerals, mainly arsenopyrite, has occurred in the laminated schist alteration zones and breccias. The mineralised faults formed in the hinge of a northwest-trending post-metamorphic antiform, and the faults may have been localised by zones of weakness associated with kink folding in the hinge of the antiform. Hydrothermal fluids responsible for mineralisation were channelled by the normal faults. These faults developed by coalescence of extensional fractures in the schist rock mass during middle Cretaceous regional extensional unroofing of the Otago Schist belt. The location of these mineralised faults near the margin of the Otago Schist belt suggests a genetic relationship between mineralisation and the regional northwest-striking normal fault systems that cut and define the schist margin.

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Lamprophyre dike intrusion and the age of the Alpine fault, New Zealand

Cited by 187 publications

References 0 publications

Crustal structure and thermal anomalies of the Dunedin Region, South Island, New Zealand

Crustal structure and thermal anomalies of the Dunedin Region, South Island, New Zealand

Magmatism during Gondwana break-up: new geochronological data from Westland, New Zealand

Structural and lithological controls on gold mineralisation at Oturehua on the northeastern margin of the Otago Schist, New Zealand

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