Relationships between the brook street Terrane and Median Tectonic Zone (Median Batholith): Evidence from Jurassic conglomerates

Permian-Jurassic ultramafic to felsic intrusive complexes at Bluff Peninsula and in the southern Longwood Range along the Southland coast represent a series of intraoceanic magmatic arcs with ages spanning a time interval of 110 m.y. New SHRIMP U-Pb zircon data for a quartz diorite from the Flat Hill complex, Bluff Peninsula, yield an age of 259 ± 4 Ma, consistent with other geochronological and paleontological evidence confirming a Late Permian age. The new data are consistent with an age of c. 260 Ma for the intrusive rocks of the Brook Street Terrane. SHRIMP U-Pb zircon ages for the southern Longwood Range confirm that intrusions become progressively younger from east to west across the complex. A gabbro at Oraka Point (eastern end of coastal section) has an age of 245 ± 4 Ma and shows virtually no evidence of zircon inheritance. The age is significantly different from that of the Brook Street Terrane intrusives. Zircon ages from the western parts of the section are younger and more varied , indicating more complex magmatic histories. A leucogabbro dike from Pahia Point gives the youngest emplacement age of 142 Ma, which is similar to published U-Pb zircon ages for the Anglem Complex and Paterson Group on Stewart Island.

Section: Bluff (C 260 Ma)supporting

confidence: 51%

Section: Sr-nd Isotopesmentioning

confidence: 99%

Section: °E 170°ementioning

confidence: 99%

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SHRIMP ion probe zircon geochronology and Sr and Nd isotope geochemistry for southern Longwood Range and Bluff Peninsula intrusive rocks of Southland, New Zealand

Price

Ireland

Maas

et al. 2006

“…Metamorphism of these rocks appears to increase from east to west. Thus, Barretts Formation overlying Brook Street Terrane is zeolite facies ; Rainy River Conglomerate overlying Triassic Buller Diorite contains chlorite-prehnite (Tulloch et al 1999); Early Cretaceous Largs Terrane (Mortimer et al 1999b) is prehnite-pumpellyite (Williams 1978). These sequences indicate that parts of the batholith, as presently exposed, were at the surface in the Jurassic and were then subjected to significant burial (greater in the west) and exhumation during the Cretaceous.…”

Section: Median Batholithmentioning

confidence: 98%

Emplacement depths of Paleozoic‐Mesozoic plutons from western New Zealand estimated by hornblende‐AI geobarometry

Tulloch

Challis

2000

Self Cite

Emplacement depths of 33 rocks from 27 Paleozoic and Mesozoic plutons from western New Zealand have been estimated utilising the hornblende-AI barometer of Anderson and Smith. Emplacement depths for plutons from the Median Batholith/Median Tectonic Zone (Median and Separation Point Suites) plutons range from 8 to 27 km. The greatest emplacement depths are found along the western edge of the batholith, in areas dominated by plutons of the Separation Point Suite; together with geochronological data they suggest significant uplift in the interval 118 to c. 110 Ma. Emplacement depths of c. 8-10 km are typical along the eastern side of the batholith in mainly Triassic plutons. No trend along the length of the batholith is apparent. Plutons associated within the lower plates of metamorphic core complexes were emplaced in the range 19-23 km, and were uplifted over a similar, but possibly slightly later, time interval. No significant consistent difference in amphibole type or chemistry was observed between the suites. Epidote believed to be of magmatic origin occurs in 11 plutons which record emplacement pressures of 3.1 kbar or greater, in conflict with the notion that such epidote indicates pluton emplacement pressures 6-8 kbar.

“…However, some authors have also treated New Zealand Jurassic sedimentary rocks as fragments of once much larger and potentially interconnected basins (Cook et al 1999a,b;Tulloch et al 1999;kear & Mortimer 2003;Uruski et al 2003;Uruski & Baillie 2004). in this scenario, Jurassic strata of the Murihiku Terrane extend beyond the traditionally accepted terrane boundaries to trangress east into adjacent Waipapa Terrane (Morrinsville facies) and Brook Street Terrane (Barretts Formation) and west into Median Batholith enclaves such as Paterson Group, Largs Group, Rainy River Conglomerate, and Drumduan Group (see Mortimer et al 1999 for details).…”

Section: Murihiku Terrane Correlationmentioning

confidence: 99%

Correlation of basement rocks from Waka Nui‐1 and Awhitu‐1, and the Jurassic regional geology of Zealandia

Mortimer¹,

Raine

Cook³

2009

Self Cite

Core and cuttings of sandstone and mudstone from Waka Nui-1, an offshore oil exploration well west of Northland, and from Awhitu-1, a water bore in western Auckland, add to the growing number of samples retrieved from otherwise inaccessible basement of the Zealandia continent. On the basis of pollen and spores, the sedim entary rocks at the bottom of Waka Nui-1 are dated as Early-Middle Jurassic, and rocks from Awhitu-1 are Late Jurassic. On the basis of age, sandstone petrology, and geographic position, a correlation of rocks in both wells with Murihiku Terrane is probable. In New Zealand, Jurassic sedimentary rocks have usually been interpreted in a tectonostratigraphic terrane context. An alternative way to look at the New Zealand Late Jurassic to Early Cretaceous sedimentary rocks is as potentially interconnected forearc, intra-arc, back-arc, and intracontinental basins that evolved adjacent to an active margin.