The Dimra Pahar Pluton is composed of arfvedsonite ± aegirine - alkali-feldspar granites with homophanous and mylonitic features. The pluton was emplaced along a regional shear zone during the post-collisional stage of the orogeny. Arfvedsonite and aegirine crystallized after alkali feldspar and quartz. The rocks are slightly peraluminous (alkali-index – AI: 0.92) to peralkaline (AI: 1.11). The pluton was emplaced at shallow depth at around 2–3 kbar pressure. The zircon saturation temperature varies between 889 and 1071 °C which is consistent with the liquidus temperature of the granitic melt. However, somewhat lower temperatures of crystallization of zircons (822–836 °C) were obtained by Ti-in-zircon thermometer. Two feldspar thermometry yields crystallization temperature ranging from 647 to 705 °C. F-free arfvedsonite crystallized at around 670 °C. Aegirine also crystallized around 670 °C. Arfvedsonite and aegirine crystallization indicates near solidus temperature of the magma. Zr-poor nature of both arfvedsonite and aegirine and presence of discrete zircon crystals suggest high oxygen fugacity of the magma. During the crystallization of zircon (near liquidus condition of the magma), the oxygen fugacity fluctuated around QFM buffer (ΔQFM = −1.22 to +1.29) as indicated by the Ce-anomalies in zircon. Later on, during the crystallization of arfvedsonite (near solidus condition of the magma), the granitic melt achieved oxygen fugacity condition above QFM buffer as indicated by the high Fe 3+ /(Fe 2+ +Fe 3+ ) ratios (0.2–0.23) of arfvedsonites. High Si/(Na + Fe + Si) ratios (0.52–0.57) of these arfvedsonites also suggest that oxygen fugacity reached above the NNO buffer during the later stage of crystallization. Pseudosection analysis of the studied rocks suggests that the mineral assemblage was equilibrated within the temperature range from 505 to 515 °C and oxygen fugacity range from −19 to −23 log units (bar), i.e. above NNO-buffer. The nearly Ti-free aegirines crystallized in highly oxidized condition near HM buffer. The development of coronal aegirine around arfvedsonite indicates the crystallization following an oxidizing path, towards the HM buffer. Water content of the granitic melt during crystallization of quartz and feldspar is estimated to be around 6 wt%. During the crystallization of arfvedsonite water content of the melt came down to 0.02 wt%. The high oxidation state and water saturated parental melts of the Dimra Pahar granite require a highly oxidized, hydrated source for the melts. A subduction-modified, metasomatically enriched lithospheric mantle or asthenospheric mantle can be considered as the source for the basaltic parental melt of Dimra Pahar granite.

中文翻译：

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印度 Hazaribagh Dimra Pahar 的 Grenvillian arfvedsonite 花岗岩结晶的物理化学条件：对可能源区的限制

Dimra Pahar Pluton 由具有同质和糜棱质特征的 arfvedsonite ± aegirine - 碱长石花岗岩组成。在造山运动的后碰撞阶段，岩体沿着区域剪切带被安置。Arfvedsonite 和 aegirine 在碱长石和石英之后结晶。岩石略微过铝（碱指数 - AI：0.92）至过碱性（AI：1.11）。岩体在大约 2-3 kbar 的压力下被放置在较浅的深度。锆石饱和温度在 889 到 1071 °C 之间变化，这与花岗岩熔体的液相线温度一致。然而，锆石中的钛温度计获得了较低的锆石结晶温度（822-836°C）。两种长石测温法得出的结晶温度范围为 647 至 705 °C。不含 F 的阿弗维钠石在 670 °C 左右结晶。Aegirine也在670°C左右结晶。Arfvedsonite 和 aegirine 结晶表明岩浆接近固相线温度。arfvedsonite 和 aegirine 的贫锆性质以及离散锆石晶体的存在表明岩浆的氧逸度较高。在锆石结晶过程中（岩浆的接近液相线条件），氧逸度在 QFM 缓冲液附近波动（ΔQFM = -1.22 至 +1.29），如锆石中的 Ce 异常所示。后来，在阿弗维钠石结晶过程中（岩浆的近固相线条件），花岗岩熔体达到了 QFM 缓冲以上的氧逸度条件，如高 Fe 3+ /(Fe 2+ +Fe 3+ ) 比 (0.2–0.23) ）的arfvedsonites。高 Si/(Na + Fe + Si) 比率 (0.52–0. 57) 这些 arfvedsonites 还表明，在结晶后期，氧逸度达到了 NNO 缓冲液以上。所研究岩石的伪剖面分析表明，矿物组合在 505 至 515 °C 的温度范围内和氧逸度范围从 -19 至 -23 log 单位 (bar) 之间达到平衡，即高于 NNO 缓冲液。几乎不含 Ti 的 aegirine 在 HM 缓冲液附近的高度氧化条件下结晶。围绕 arfvedsonite 的日冕 aegirine 的发展表明结晶遵循氧化路径，朝向 HM 缓冲液。在石英和长石结晶过程中，花岗岩熔体的含水量估计约为 6%（重量）。在阿维钠石结晶过程中，熔体的水含量降至 0.02 重量％。Dimra Pahar 花岗岩的高氧化态和水饱和母熔体需要高度氧化、水合的熔体来源。俯冲改造的、交代富集的岩石圈地幔或软流圈地幔可以被认为是 Dimra Pahar 花岗岩玄武质母熔体的来源。