Reconnaissance thermochronology of southern Zealandia
Reconnaissance thermochronology of southern Zealandia
复制标题
西兰大陆南部勘测热年代学
DOI：
--
复制
发表时间：
2015
影响因子：
2.7
通讯作者：
A. Tulloch
中科院分区：
文献类型：
--
作者：
N. Mortimer;B. Kohn;D. Seward;T. Spell;A. Tulloch
我们报告新的裂变径迹，（U-Th）/He和40 Ar/39 Ar年龄的矿物表面，疏浚和钻孔岩屑样品从南岛南部，坎贝尔高原和查塔姆上升地区的西兰迪亚大陆。我们的研究结果表明，南部西兰迪亚经历了快速冷却的时间间隔105-80马，可能在广泛的陆内裂谷西兰迪亚从冈瓦纳分裂之前。然而，查塔姆片岩中锆石He保留带的108 ± 11 Ma快速折返可能记录了冈瓦纳边缘由于希库朗吉高原碰撞和/或伸展裂谷幕的开始而停止的长期俯冲。在当地，基底岩石已明显加热，热年代学系统复位，在大南盆地的深化和当地中新世板内火山活动。采自坎贝尔高原南端前寒武纪花岗岩的磷灰石裂变径迹年龄为179 ± 17 Ma，表明其可能为冰筏沉积，因此西兰迪亚前寒武纪地壳的原位存在尚未得到证实。与此相反，来自共轭南极大陆边缘Iselin Bank的前寒武纪变流纹岩的锆石（U-Th）/He年龄为99 ± 9 Ma，表明可能是原地位置。补充材料：详细的分析方法和原始数据见：http://www.geolsoc.org.uk/SUP18886。
We report new fission-track, (U–Th)/He and 40Ar/39Ar ages for minerals in surface, dredge and borehole cuttings samples from the southern South Island, Campbell Plateau and Chatham Rise regions of the Zealandia continent. Our results indicate that much of southern Zealandia underwent rapid cooling in the interval 105–80 Ma, probably during widespread intracontinental rifting before Zealandia split from Gondwana. The 108 ± 11 Ma rapid exhumation of a zircon He retention zone in the Chatham Schist, however, may record cessation of long-lived subduction at the Gondwana margin owing to Hikurangi Plateau collision and/or the onset of the extensional rifting episode. Locally, basement rocks have been appreciably heated, and thermochronological systems reset, in response to deepening of the Great South Basin and by local Miocene intraplate volcanism. An apatite fission-track age of 179 ± 17 Ma from a dredge sample of Precambrian granite at the southern tip of the Campbell Plateau indicates that it is probably ice-rafted, thus in situ Precambrian crust in Zealandia is still unconfirmed. In contrast, a zircon (U–Th)/He age of 99 ± 9 Ma from a Precambrian metarhyolite from Iselin Bank at the conjugate Antarctic continental margin plausibly indicates an in situ position. Supplementary material: Detailed analytical methods and raw data are available at: http://www.geolsoc.org.uk/SUP18886.