摘要
大氧化事件(Great Oxidation Events, GOE)的记录主要是来自于沉积岩地球化学特征,岩浆岩方面的证据较少。然而,全球弧岩浆岩的Th/U比值成功指示了两次大氧化事件,开创了利用岩浆岩地球化学指标探索大氧化事件研究的新领域。弧岩浆岩通常产生于俯冲洋壳脱水交代的上覆地幔楔部分熔融,具有重稀土较富集的特点。本研究结合弧岩浆岩相关研究成果,探讨大氧化事件前后不同时期TTG(tonalite-trondhjemite-granodiorite)岩浆岩是否可以记录GOE,以及GOE对TTG的形成会产生哪些影响,特别是后者,前人在考虑大氧化事件期间及之后的TTG形成时,往往忽略了这一影响。通过锆石年代学证明,在2.45~2.20 Ga(全球岩浆静寂期)范围内,针对不同时期(2.43~2.18 Ga)的明显受表壳物质(锆石Hf-O同位素佐证)加入影响的TTG岩石开展研究,包括其锆石Th/U比值和锆石氧逸度异常,为探讨GOE对不同深度岩浆岩的影响提供了新证据。研究表明,三类不同时期的TTG岩石主微量元素与高硅埃达克岩具有相似的地球化学特征。此外,GOE对不同时期岩浆作用的氧同位素和氧逸度变化有一个升高再降低的过程。全岩花岗岩构造图解和锆石微量元素表明这些岩石形成于大洋俯冲带岛弧环境,这一形成过程可能是由于俯冲洋壳脱水和熔融,随后导致TTG岩石氧逸度发生变化。
The majority of records pertaining to the Great Oxidation Events(GOE)are derived from the geochemical characteristics of sedimentary rocks,with minimal involvement of evidence from igneous rocks.However,the Th/U ratio of global arc magmatic rocks has successfully identified two instances of the GOE,opening a new avenue of research using igneous rock geochemical indicators to explore this phenomenon.Arc magmatic rocks generally form through the melting of the overlying mantle wedge during subduction-induced dehydration of oceanic crust,exhibiting enrichment in heavy rare earth elements.Building on the findings from studies of arc magmatic rocks,this paper investigates whether TTG(tonalite-trondhjemite-granodiorite)magmatic rocks from different periods can record the GOE and examines the impact of the GOE on TTG formation.This is particularly significant given that previous studies have often overlooked this influence when considering the formation of TTG during and after the Great Oxidation Events.Through zircon geochronology,within the range of 2.45~2.20 Ga(tectonomagmatic lull),this study demonstrates TTG rocks influenced by the addition of crustal material during different periods(2.43~2.18 Ga),incorporating evidence from zircon Th/U ratios and zircon oxygen fugacity anomalies.This provides new insights into the impact of the GOE on magmatic rocks at different depths.Research has shown that the major and trace elements in TTG rocks from three distinct periods exhibit geochemical characteristics similar to high-silica adakites.Additionally,the Great Oxidation Event(GOE)reveals a pattern of increasing,then decreasing,oxygen isotope and oxygen fugacity changes throughout various periods of magmatic activity.Structural diagrams of whole-rock granite and trace elements of zircon suggest that TTG rocks were formed within an island arc environment situated along an oceanic subduction zone.This formation process is hypothesized to result from the dehydration and melting of the subducted oceanic crust,leading to variations in the oxygen fugacity of TTG rocks.
作者
刘恒
刘磊
张创业
LIU Heng;LIU Lei;ZHANG Chuangye(Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring,Central South University,Changsha,Hunan 410083,China;School of Geosciences and Info-Physics,Central South University,Changsha,Hunan 410083,China)
出处
《地质学报》
北大核心
2025年第8期2634-2654,共21页
Acta Geologica Sinica
基金
国家自然科学基金项目(编号41972198)
湖南省自然科学基金项目(编号2022JJ30702)
中南大学研究生自主探索创新项目(编号2023ZZTS0439)
国家留学基金项目(编号CSC202306370128)联合资助的成果。
关键词
大氧化事件
氧逸度
华北克拉通南缘
锆石Hf-O同位素
Great Oxidation Events
oxygen fugacity
south margin of the North China Craton
zircon Hf-O isotopes
