U–Pb geochronology of Permian plutonic rocks, Longwood Range, New Zealand: implications for Median Batholith–Brook Street Terrane relations
U–Pb geochronology of Permian plutonic rocks, Longwood Range, New Zealand: implications for Median Batholith–Brook Street Terrane relations
复制标题
新西兰朗伍德山脉二叠纪深成岩的 U-Pb 年代学：对中基岩-布鲁克街地体关系的影响
DOI：
10.1080/00288306.2013.869235
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发表时间：
2014
影响因子：
2.2
通讯作者：
T. Ireland
中科院分区：
文献类型：
--
作者：
AJ McCoy;N. Mortimer;T. Ireland
本文报道了长木岭辉长岩和相关侵入岩的U-Pb高分辨离子探针（SHRIMP）锆石年龄。在层状含铂的赫克亚辉长岩中获得了257.6 ± 2.5Ma、256.5 ± 1.8Ma和251.6 ± 2.0Ma的锆石U-Pb年龄（2σm）。这是5-10 Ma以上的冷却年龄以前获得的Ar-Ar年龄的角闪石。本文报道了Pourakino西部奥长花岗岩的锆石U-Pb年龄为252.8 ± 2.7Ma [207 Pb/206 Pb热电离质谱法测得的年龄为292 ± 8 Ma]，切割Hekeia辉长岩的奥长花岗岩脉的年龄为254.8 ± 2.6Ma。我们新的锆石年龄表明，Hekeia辉长岩和Pourakino Trondhjemite侵入在相同的，相对较窄的间隔从261至252 Ma。这一年龄范围比早二叠世（c。276-288 Ma）的年龄推断的主要Takitimu组火山活动在邻近的布鲁克街地体的化石证据。我们提出了新的建议，Hekeia和Pourakino机构，沿着与岩体在海崖和Oraka点，构成了一个新的长木套房的中位岩，在空间和时间上不同于异地布鲁克街地体火山岩浆作用。长木岭西部花岗闪长岩的锆石U-Pb年龄为232.3 ± 1.5 Ma，是迄今为止已知的最古老的Darran Suite岩体，代表了一个主要的、同位素更演化的中粒岩脉冲的开始。
We present U–Pb sensitive high-resolution ion microprobe (SHRIMP) zircon ages from gabbros and associated intrusive rocks of the Longwood Range, Southland. U–Pb zircon ages of 257.6 ± 2.5 Ma, 256.5 ± 1.8 Ma and 251.6 ± 2.0 Ma (2σm) have been obtained from the layered, platiniferous Hekeia Gabbro. These are 5–10 Ma older than cooling ages previously obtained by Ar–Ar dating of hornblendes. A revised U–Pb zircon age of 252.8 ± 2.7 Ma is reported for a sample of western Pourakino Trondhjemite [previously dated at 292 ± 8 Ma by multicrystal 207Pb/206Pb thermal ionization mass spectrometry (TIMS) methods] and a dike of the trondhjemite that cuts the Hekeia Gabbro is dated at 254.8 ± 2.6 Ma. Our new zircon ages show that the Hekeia Gabbro and Pourakino Trondhjemite were intruded within the same, relatively narrow interval from 261 to 252 Ma. This age range is substantially younger than Early Permian (c. 276–288 Ma) ages inferred from fossil evidence of major Takitimu Group volcanism in the adjacent Brook Street Terrane. We make the novel suggestion that the Hekeia and Pourakino bodies, along with plutons at Bluff and Oraka Point, constitute a new Longwood Suite of the Median Batholith that is spatially and temporally distinct from allochthonous Brook Street Terrane volcanic magmatism. A U–Pb zircon age of 232.3 ± 1.5 Ma from a western Longwood Range granodiorite is the oldest Darran Suite pluton so far recognized and represents the start of a major, isotopically more evolved, pulse of the Median Batholith.