罗丁石
罗丁岩（英语：Rodingite）是由钙铁榴石、钙辉石(calcic pyroxene)、符苏岩(vesuvianite)、绿帘石和方柱石(scapolite)组成的交代变质岩 [1]。 主要产于镁铁质岩石靠近蛇纹石化的超镁铁质岩石的地方。 当超镁铁质岩石被镁铁质岩石被蛇纹石化时，所排除的流体副产品含高 pH 值、Ca2+ 和 OH- ，与镁铁质岩石接触后，发生交代变质作用，而造罗丁岩[2][3]，罗丁岩的矿物组成变化很大，但都具有高钙、和低硅的特征[4]。 罗丁岩产出最多的地方是蛇绿岩、蛇纹岩混杂岩、海底橄榄岩和榴辉岩地区中。 罗丁岩是根据在新西兰，罗丁河出露的顿山蛇绿岩带的露头而命名[5]。
罗丁石化[编辑]
罗丁石化的过程是渐变的。例如在蛇绿岩中的捕虏岩， 其中榴辉岩的罗丁石化 ，从体积，矿物组成，化学成分及纹理都呈现出连续变化。完全被罗丁石化的岩石，其矿物的组合与原岩差异很大[6][7]。
全球元素循环[编辑]
罗丁石化是全球元素循环重要作用之一。它能消除洋壳在变质时大量产出的的Ca。由于洋壳在地球表面的广汎分布，海洋岩石圈的超镁铁质岩在被石蛇纹岩化时，会释出大量Ca。 而罗丁岩的形成就能吸收这些Ca。保持Ca元素在全球的平衡。罗丁岩中的稳定Ca 和放射性 Sr 同位素的组成，与地幔特征相似，因此可证明罗丁石的 Ca 和 Sr 来自地幔 [8]。
参考文献[编辑]
- ^ Fettes, Douglas; Desmons, Jacqueline (2007). Metamorphic Rocks - A Classification and Glossary of Terms. Cambridge University Press.
- ^ Laborda-López, Casto; López-Sánchez-Vizcaíno, Vicente; Marchesi, Claudio; Gómez-Pugnaire, María Teresa; Garrido, Carlos J.; Jabaloy-Sánchez, Antonio; Padrón-Navarta, José A.; Hydas, Károly (2018). "High‐P metamorphism of rodingites during serpentinite dehydration (Cerro del Almirez, Southern Spain): Implications for the redox state in subduction zones". Journal of Metamorphic Geology. 36: 1141–1173. doi:10.1111/jmg.12440.
- ^ Salvioli-Mariani, Emma; Boschetti, Tiziano; Toscani, Lorenzo; Montanini, Alessandra; Petriglieri, Jasmine Rita; Bersani, Danilo (2020). "Multi-stage rodingitization of ophiolitic bodies from Northern Apennines (Italy): Constraints from petrography, geochemistry and thermodynamic modelling". Geoscience Frontiers. 11: 2103–2125. doi:10.1016/j.gsf.2020.04.017.
- ^ Python; Marie; Masako; Yoshikawa; Tomoyuki Shibata; Shoji Arai (2011). Dyke swarms: Keys for geodynamic interpretation. Berlin, Heidelberg: Springer. pp. 401–435. Bibcode:2011dskg.book.....S.
- ^ Johnston, M. R. (2007). "Nineteenth-century observations of the Dun Mountain Ophiolite Belt, Nelson, New Zealand and trans-Tasman correlations". Geological Society, London, Special Publications. 287 (1): 375–387. Bibcode:2007GSLSP.287..375J. doi:10.1144/sp287.27.
- ^ LI, X.-P., ZHANG, L., WEI, C., AI, Y. and CHEN, J. (2007), Petrology of rodingite derived from eclogite in western Tianshan, China. Journal of Metamorphic Geology, 25: 363-382. https://doi.org/10.1111/j.1525-1314.2007.00700.x
- ^ Barriga, F., Fyfe, W.S. Development of rodingite in basaltic rocks in serpentinites, East Liguria, Italy. Contr. Mineral. and Petrol. 84, 146–151 (1983). https://doi.org/10.1007/BF00371281
- ^ Nikolaus Gussone, Håkon Austrheim, Anne Westhues, Klaus Mezger(2020), Origin of Rodingite Forming Fluids Constrained by Calcium and Strontium Isotope Ratios in the Leka Ophiolite Complex, Chemical Geology, Volume 42, , 119598, ISSN 0009-2541, https://doi.org/10.1016/j.chemgeo.2020.119598. (https://www.sciencedirect.com/science/article/pii/S0009254120301376)