Conditions of Archean granulite metamorphism in the Godthab-Fiskenaesset region, southern West Greenland
Conditions of Archean granulite metamorphism in the Godthab-Fiskenaesset region, southern West Greenland
复制标题
DOI：
10.1111/j.1525-1314.1990.tb00464.x
复制
发表时间：
1990-03
影响因子：
3.4
通讯作者：
L. Riciputi;J. Valley;V. R. Mcgregor
中科院分区：
文献类型：
--
作者：
L. Riciputi;J. Valley;V. R. Mcgregor
西格陵兰南部的Nordlandet半岛和Tasiusarsuaq半岛分别在3.0和2.8 Ga变质为麻粒岩相。用磁铁矿+钛铁矿、石榴石+斜方辉石、石榴石+单斜辉石和石榴石+黑云母温度计估算了变质作用温度。在这两个实验室中使用了八个不同的石榴石气压计进行了气压测量。对每一个气压计都采用了一套统一的所有矿物的活动模式，包括牛顿等人（1986年）的石榴石活动模式，以便进行比较。使用不同气压计的压力估计值通常相当一致（±1.5千巴）。使用Newton等人（1986）的石榴石活动数据得出的压力与使用其他石榴石活动模型得出的压力相似。据估计，Nordlandet半岛的峰值变质条件为800 ± 50°C，7.9 ± 1.0 kbar。logfO2值估计为1.1至2.0以上的石英+磁铁矿+铁橄榄石缓冲磁铁矿+钛铁矿和石英+磁铁矿+硅铁组合。据估计，Tasiusarsuaq的峰值变质条件为780 ± 50°C，8.9 ± 1.0 kbar。估计fH2O和fCO2使用黑云母，角闪石，钙铝榴石+钙长石和钙铝榴石+方柱石平衡都很低，在这两个岩石。这些结果表明，麻粒岩变质是流体缺席的两个火山岩，变质作用在Akia火山岩，也可能在Tasiusarsuaq火山岩是由大量的岩浆注入到下地壳。
The Nordlandet peninsula (Akia terrane) and the Tasiusarsuaq terrane in southern West Greenland were metamorphosed to granulite facies at 3.0 and 2.8 Ga respectively. Temperatures of metamorphism are estimated using magnetite + ilmenite, garnet + orthopyroxene, garnet + clinopyroxene and garnet + biotite thermometers. Barometry has been carried out in the two terranes using eight different garnet barometers. A uniform set of activity models for all minerals, including the garnet activity model of Newton et al. (1986), is applied to each barometer in order to permit comparison. Pressure estimates using the different barometers are generally quite consistent (±1.5 kbar). Use of the Newton et al. (1986) garnet activity data results in pressures similar to those obtained using other garnet activity models. Peak metamorphic conditions on the Nordlandet peninsula are estimated to have been 800 ± 50°C, 7.9 ± 1.0 kbar. Values of logfO2 are estimated to have been 1.1 to 2.0 above the quartz + magnetite + fayalite buffer from assemblages of magnetite + ilmenite and quartz + magnetite + ferrosilite. Peak metamorphic conditions in the Tasiusarsuaq terrane are estimated to have been 780 ± 50°C, 8.9 ± 1.0 kbar. Estimates of fH2O and fCO2 using biotite, amphibile, grossular + anorthite and grossular + scapolite equilibria are low in both terranes. These results suggest that granulite metamorphism was fluid absent in both terranes, and that the metamorphism in the Akia terrane and possibly also in the Tasiusarsuaq terrane was initiated by the injection of large volumes of magma into the lower crust.