Temporal links between pluton emplacement, garnet granulite metamorphism, partial melting and extensional collapse in the lower crust of a Cretaceous magmatic arc, Fiordland, New Zealand
Temporal links between pluton emplacement, garnet granulite metamorphism, partial melting and extensional collapse in the lower crust of a Cretaceous magmatic arc, Fiordland, New Zealand
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DOI：
10.1111/jmg.12064
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发表时间：
2014-02
影响因子：
3.4
通讯作者：
H. Stowell;K. O. Parker;M. Gatewood;A. Tulloch;Alan E. Koenig
中科院分区：
文献类型：
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作者：
H. Stowell;K. O. Parker;M. Gatewood;A. Tulloch;Alan E. Koenig
新西兰峡湾的石榴麻粒岩相中下地壳提供了岩浆弧中下地壳发生脉冲侵入和变形的证据。238 U-206 Pb锆石年龄将面积为595 km 2的Malaspina岩体的侵位时间限制在116-114 Ma。9个Sm-Nd石榴石年龄（多点石榴石-岩石等时线），范围为115.6 ± 2.6 ~ 110.6 ± 2.0 Ma，表明整个岩体的石榴麻粒岩相变质作用是同步或近同步的。因此，部分熔融和石榴子石麻粒岩相变质作用持续了900 °C，石榴子石中含有约4000 ppm的Ti;随后，金红石包裹体在温度下降和压力变化有限的情况下生长。Malaspina岩体的石榴麻粒岩变质作用为c。比北方峡湾彭布罗克麻粒岩的类似变质作用年轻10 Ma;因此，对于这片>3000 km²的中下地壳区域，高磷变质作用和部分熔融一定是穿时发生的。因此，白垩纪冈瓦纳弧下地壳根轴沿着由北向南发生了两次或两次以上的侵入脉冲，紧接着石榴麻粒岩变质和伸展应变。
Garnet granulite facies mid‐to lower crust in Fiordland, New Zealand, provides evidence for pulsed intrusion and deformation occurring in the mid‐to lower crust of magmatic arcs. 238U‐206Pb zircon ages constrain emplacement of the ∼595 km2 Malaspina Pluton to 116–114 Ma. Nine Sm‐Nd garnet ages (multi‐point garnet‐rock isochrons) ranging from 115.6 ± 2.6 to 110.6 ± 2.0 Ma indicate that garnet granulite facies metamorphism was synchronous or near synchronous throughout the pluton. Hence, partial melting and garnet granulite facies metamorphism lasted 900 °C, garnet contained ∼4000 ppm Ti; subsequently, rutile inclusions grew during declining temperature with limited pressure change. Garnet granulite metamorphism of the Malaspina Pluton is c. 10 Ma younger than similar metamorphism of the Pembroke Granulite in northern Fiordland; therefore, high‐P metamorphism and partial melting must have been diachronous for this >3000 km² area of mid‐to‐lower crust. Thus, two or more pulses of intrusion shortly followed by garnet granulite metamorphism and extensional strain occurred from north to south along the axis of the lower crustal root of the Cretaceous Gondwana arc.