Petrology and phase equilibrium modeling of sapphirine + quartz assemblage from the Napier Complex, East Antarctica: diagnostic evidence for Neoarchean ultrahieh-temperature metamorohism
Petrology and phase equilibrium modeling of sapphirine + quartz assemblage from the Napier Complex, East Antarctica: diagnostic evidence for Neoarchean ultrahieh-temperature metamorohism
复制标题
东南极洲纳皮尔杂岩蓝宝石石英组合的岩石学和相平衡模型：新太古代超高温变质作用的诊断证据
DOI：
10.1016/j.gsf.2012.09.001
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发表时间：
2013
影响因子：
8.9
通讯作者：
Hisako Shimizu
中科院分区：
文献类型：
--
作者：
R.Ishii;A.Kaneta;R.G.Banal;M.Funato;Y.Kawakami;Hisako Shimizu
综合南极东部纳皮尔杂岩Tonagh岛（TI）和Priestley峰（PP）两个地点含平衡蓝宝石+石英组合的麻粒岩相岩的岩石学特征，为新太古代可能与碰撞造山运动有关的地壳极端变质提供了明确的证据。不同样品中与蓝宝石+石英相关的反应微观结构存在差异，可能反映了变质演化过程中不同的构造条件。TI样品中的蓝宝石和石英可能在峰值阶段处于平衡状态，但现在被Grt + Sil + Opx的日冕分离，表明在峰值变质作用后接近等压冷却，而PP样品中的石榴石则被Spr + Qtz + Sil + Crd + Spl组合取代，表明峰后减压。在NCKFMASHTO体系中应用矿物平衡模型表明，由于岩石中Fe3+含量较低（Fe2O3/(FeO + Fe2O3)摩尔数= 0.02），Spr + Qtz稳定性降低至930℃。TI样品产生950-1100°C和7.5-11 kbar的峰值范围，随后冷却到800-950°C和8-10 kbar的逆行阶段，可能沿着逆时针路径。相比之下，PP样品的峰值条件为1000-1050°C和>12 kbar，随后在930-970°C和6.7-7.7 kbar的温度下，在石榴石周围形成了Spr + Qtz日冕，表明可能沿顺时针- t轨迹减压。这种对比的p-路径与最近关于纳皮尔杂岩构造框架的模型是一致的，该模型将这两个地区与不同的地壳块体联系起来。从两个地区获得的不同路径可能反映了在一个复杂的新太古代俯冲/碰撞带中这些岩石的构造格局的差异。
A synthesis of the petrological characters of granulite facies rocks that contain equilibrium sapphirine + quartz assemblage from two localities (Tonagh Island (TI) and Priestley Peak (PP)) in the Napier Complex, East Antarctica, provides unequivocal evidence for extreme crustal metamorphism possibly associated with the collisional orogeny during Neoarchean. The reaction microstructures associated with sapphirine + quartz vary among the samples, probably suggesting different tectonic conditions during the metamorphic evolution. Sapphirine and quartz in TI sample were probably in equilibrium at the peak stage, but now separated by corona of Grt + Sil + Opx suggesting near isobaric cooling after the peak metamorphism, whereas the Spr + Qtz + Sil + Crd + Spl assemblage replaces garnet in PP sample suggesting post-peak decompression. The application of mineral equilibrium modeling in NCKFMASHTO system demonstrated that Spr + Qtz stability is lowered down to 930 °C due to small Fe3+contents in the rocks (mole Fe2O3/(FeO + Fe2O3) = 0.02). The TI sample yields a peakp-Trange of 950–1100 °C and 7.5–11 kbar, followed by cooling toward a retrograde stage of 800–950 °C and 8–10 kbar, possibly along a counterclockwisep-Tpath. In contrast, the peak condition of the PP sample shows 1000–1050 °C and >12 kbar, which was followed by the formation of Spr + Qtz corona around garnet at 930–970 °C and 6.7–7.7 kbar, suggesting decompression possibly along a clockwisep-Ttrajectory. Such contrastingp-Tpaths are consistent with a recent model on the structural framework of the Napier Complex that correlates the two areas to different crustal blocks. The differentp-Tpaths obtained from the two localities might reflect the difference in the tectonic framework of these rocks within a complex Neoarchean subduction/collision belt.