羅丁石
羅丁岩（英語：Rodingite）是由鈣鐵榴石、鈣輝石(calcic pyroxene)、符蘇岩(vesuvianite)、綠簾石和方柱石(scapolite)組成的交代變質岩 [1]。 主要產於鎂鐵質岩石靠近蛇紋石化的超鎂鐵質岩石的地方。 當超鎂鐵質岩石被鎂鐵質岩石被蛇紋石化時，所排除的流體副產品含高 pH 值、Ca2+ 和 OH- ，與鎂鐵質岩石接觸後，發生交代變質作用，而造羅丁岩[2][3]，羅丁岩的礦物組成變化很大，但都具有高鈣、和低矽的特徵[4]。 羅丁岩產出最多的地方是蛇綠岩、蛇紋岩混雜岩、海底橄欖岩和榴輝岩地區中。 羅丁岩是根據在新西蘭，羅丁河出露的頓山蛇綠岩帶的露頭而命名[5]。
羅丁石化
羅丁石化的過程是漸變的。例如在蛇綠岩中的捕虏岩， 其中榴輝岩的羅丁石化 ，從體積，礦物組成，化學成分及紋理都呈現出連續變化。完全被羅丁石化的岩石，其礦物的組合與原岩差異很大[6][7]。
全球元素循環
羅丁石化是全球元素循環重要作用之一。它能消除洋殼在變質時大量產出的的Ca。由於洋殼在地球表面的廣汎分佈，海洋岩石圈的超鎂鐵質岩在被石蛇紋岩化時，會釋出大量Ca。 而羅丁岩的形成就能吸收這些Ca。保持Ca元素在全球的平衡。羅丁岩中的穩定Ca 和放射性 Sr 同位素的組成，與地幔特徵相似，因此可證明羅丁石的 Ca 和 Sr 來自地幔 [8]。
參考文獻
- ^ 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)