Abstract Dolomite is a carbonate mineral frequently found in sedimentary rocks from Proterozoic to Holocene. In the Iberian Peninsula, dolomites appear in a wide number of geological formations and they can be considered as representative of dolomites crystallised in most (post)sedimentary environments on Earth. In this paper, we present a first systematic study of the cation order of dolomites formed from Neoproterozoic to late Holocene. We found that the lowest values of cation order (quantified by measuring I01.5/I11.0 intensity ratios on diffractograms) mainly correspond to dolomites formed in about the last 30 Myr. In contrast, older dolomites usually reach maximum I01.5/I11.0 intensity ratios. Furthermore, higher values of cation order seem to be related to higher values of the full width half maximum of 10.4 diffraction peaks (FWHM10.4). Assuming that a decrease in FWHM10.4 (i.e. an increase in the crystallite size) in sedimentary environments indicates mineral ripening, our results show that Mg-Ca ordering in dolomites might take place mainly by a dissolution-(re)crystallisation ageing process operating over large geological periods.

中文翻译：

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地质记录中的白云石阳离子顺序

摘要 白云石是一种碳酸盐矿物，常见于元古代至全新世的沉积岩中。在伊比利亚半岛，白云岩出现在多种地质构造中，它们可以被认为是地球上大多数（后）沉积环境中结晶的白云岩的代表。在本文中，我们首次系统地研究了从新元古代到晚全新世形成的白云岩的阳离子序。我们发现阳离子顺序的最低值（通过测量衍射图上的 I01.5/I11.0 强度比量化）主要对应于大约最后 30 Myr 形成的白云岩。相比之下，较老的白云岩通常达到最大的 I01.5/I11.0 强度比。此外，较高的阳离子级值似乎与 10.4 衍射峰 (FWHM10.4) 的半峰全宽的较高值有关。