Exploring the preservation of alkaline-carbonatitic extrusive rocks in relation to continent formation
Exploring the preservation of alkaline-carbonatitic extrusive rocks in relation to continent formation
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探索与大陆形成相关的碱性碳酸岩喷出岩的保存
DOI：
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发表时间：
2013
期刊：
影响因子：
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通讯作者：
P. Lythgoe
中科院分区：
文献类型：
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作者：
L. S. Campbell;A. Dyer;Craig Williams;P. Lythgoe
本文研究了大陆碱性-碳酸质喷出岩的矿物反应途径。沸石伪装假设[1]。该假说认为，沸石蚀变反应是这些层状序列逐渐稳定的第一步，因为高活性火山沉积物从玻璃经沸石变成自生长石、粘土和SiO2相。报道的reactionprogress是暗示的趋势，其中Si/Al随时间增加作为更广泛的，Si饱和流体与早期形成的阶段在大陆环境中的反应。稀土元素和高场强元素在反应过程的各个阶段是如何表现的，目前还不清楚，因为对大量天然沸石中的稀土元素还没有进行系统的研究。但我们的初步数据表明，最初形成的低硅沸石（如钙十字沸石），反映了原始火山玻璃的稀土模式。随着反应的进展，暴露于更广泛的地壳流体，蚀变序列的微量元素特征很可能发生变化。其中一些修改将取决于不同沸石矿物在反应路径中的离子选择性性质，但流体控制肯定是显而易见的。初步探讨可能的例子在geologicalrecord，识别和稳定的反应序列，进行了讨论。[1]坎贝尔等人（2012）Mineralium Deposita，47，371？382.
Mineral reaction paths related to continental alkaline-carbonatiticextrusive rocks are examined in the context of a?zeolitic masquerade? hypothesis [1]. The hypothesis suggeststhat zeolitic alteration reactions are the first steps in a gradualstabilization of these bedded successions, as the highlyreactive volcanic deposits change from glasses via zeolites toauthigenic feldspars, clays and SiO2 phases. Reported reactionprogressions are suggestive of trends in which Si/Al increaseswith time as wider, Si-saturated fluids react with earlier formedphases in continental environments. It is not knownhow trace elements such as the REE and HFSE behave at eachstage of reactive progression as no systematic study of theseelements has been made for wide occurrences of naturalzeolites. But our preliminary data indicate that the first formed,low-Si zeolites (e.g. phillipsite), reflect the REEpatterns of the original volcanic glasses. Modifications to traceelement signatures of altered successions are very likely tooccur as reactions progress with exposure to wider crustalfluids. Some of these modifications will be dependent on theion-selectivity properties of different zeolite minerals in thereaction paths, but fluid controls are certainly evident. Apreliminary exploration of possible examples in the geologicalrecord, of recognition and stabilization of reactive successions,is discussed.[1] Campbell et al (2012) Mineralium Deposita, 47, 371?382.