Crystallization and resorption in plutonic plagioclase: Implications on the evolution of granodiorite magma (Gęsiniec granodiorite, Strzelin Crystalline Massif, SW Poland)
Crystallization and resorption in plutonic plagioclase: Implications on the evolution of granodiorite magma (Gęsiniec granodiorite, Strzelin Crystalline Massif, SW Poland)
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DOI：
10.1016/j.lithos.2005.05.008
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发表时间：
2006-02
期刊：
影响因子：
3.5
通讯作者：
A. Pietranik;J. Koepke;J. Puziewicz
中科院分区：
文献类型：
--
作者：
A. Pietranik;J. Koepke;J. Puziewicz
波兰西南部Strzelin结晶地块Güssiniec侵入体中的花岗闪长岩含有复杂的带状斜长石。五个化学和结构上不同的区域可以在晶体之间相互关联：“核心”（25-35%的An），内地幔（40-45%的An），外地幔（40-25%的An），吸收区（35-50%的An）和边缘（35-30%的An）。晶体之间的地带的良好的结构和化学（主要和微量元素）的相关性表明，分带是由岩浆房规模的结晶条件的变化。斜长石作为液相线相，记录了从结晶开始到花岗闪长岩作为薄岩墙侵位和快速冷却的时间跨度。结晶化开始于内地幔的形成。内地幔的缺乏和大小不一表明高温岩浆结晶缓慢。正常环带的内地幔是在过冷度增加的条件下形成的。地幔的成分趋势表明封闭系统结晶。主要的再吸收区是由注入较少演化的岩浆所造成的，如斜长石中锶的增加所示。注入引发了岩浆和斜长石晶体的快速上升，促进混合，但也诱导快速，动力学控制的复杂的多，振荡环带内吸收区的增长。岩浆上升导致斜长石减压熔融，并在地幔内部形成熔融包裹体。减压范围估计至少为2千巴。花岗闪长岩作为薄岩墙的侵位使斜长石中的岩浆分带得以快速冷却和保存。熔体包裹体在岩浆后冷却过程中完全结晶。深成斜长石的分带样式与火山斜长石明显不同，表明岩浆演化过程不同。深成斜长石中的带具有很好的相关性，表明在静止岩浆中可能发生结晶聚集和成分岩浆分层。晶体可能不会在不同的制度之间流动。吸收发生，但作为单一事件，尽管复杂。深成斜长岩带的良好相关性可以区分控制分带的主要过程和叠加的动力学效应。
Granodiorite from the Gęsiniec Intrusion, Strzelin Crystalline Massif, SW Poland contains complexly zoned plagioclases. Five chemically and structurally distinct zones can be correlated among crystals: ‘cores’ (25–35% An), inner mantles (∼40–45% An), outer mantles (40–25% An), resorption zones (35–50% An) and rims (35–30% An). Good structural and chemical (major and trace elements) correlation of zones between crystals indicates that zonation was produced by changes in conditions of crystallization on a magma chamber scale. Plagioclase, being the liquidus phase, records a time span from the beginning of crystallization to emplacement and rapid cooling of granodiorite as thin dykes. Crystallization began with the formation of inner mantles. The paucity and different sizes of inner mantles suggests slow crystallization in high temperature magma. Normally zoned inner mantles were formed under increasing undercooling. Compositional trends in mantles suggest closed system crystallization. The major resorption zones were caused by injection of less evolved magma as indicated by the strontium increase in plagioclase. The injection triggered a rapid rise of magma and plagioclase crystals facilitating mixing but also inducing fast, kinetically controlled growth of complex multiple, oscillatory zonation within resorption zones. The ascent of magma caused decompression melting of plagioclase and produced melt inclusions within inner mantles—the ‘cores’. The decompression range is estimated at a minimum of 2 kbar. Emplacement of granodiorite as thin dykes allow rapid cooling and preservation of magmatic zonation in plagioclases. Melt inclusions crystallized completely during post-magmatic cooling. The zonation styles of plutonic plagioclase differ markedly from volcanic ones suggesting different magma evolution. Zones in plutonic plagioclase are well correlated indicating crystallization in quiescent magma where crystals accumulation and compositional magma stratification may occur. Crystals probably did not travel between different regimes. Resorption occurred but as single albeit complex episodes. Good correlation of zones in plutonic plagioclases allows a distinction between the main processes controlling zonation and superimposed kinetic effects.