Massive Burial Dolomitization: The Jurassic Vajont Oolite of Northeastern Italy

块状交代白云岩的成因仍然是 沉积学中尚未解决的重大问题。 目前青睐 对大规模陨石起源的解释集中在 “早期”低温过程涉及表面或近- 地表沃茨和“晚期”掩埋等替代过程 除少数工人外，所有人都忽视了消毒。 的 理论和计算机模型的最新发展 沉积盆地中的地下水流系统使得时机成熟 重新审视埋葬消毒 流体流动是一个新的 一个重要的因素，需要添加到我们的努力 解决白云石问题。 这是一项关于白云石的研究 位于北方威尼斯阿尔卑斯山的侏罗纪瓦洪特鲕粒岩 意大利，初步的实地和地球化学工作表明， 在埋藏条件下，高温下发生了石化作用 条件 方法将是将实地工作， 岩相学、同位素和流体包裹体数据以及水文学 建模 Vajont Oolite提供了几个特殊功能， 使这样的研究值得：（1）它是大量的，但不是 彻底的反腐败， 直接线索的地下路径的液化流体 可以映射（见牛顿，哈迪和菲利普斯，1990年）;（2）它 由沉积在深水中的浅水软泥组成 蚀变前斜坡作用水，为浅水 （3）类鲕粒和它们的成矿作用; 未风化部分粒间胶结物保存完好 的Vajont sot帽子，它是可能的，以详细记录他们的 岩石学和同位素地球化学;因此， 可以识别和测量由石化产生的变化; (4)部分但大规模破产的Vajont在 道路开挖表明，石化流体通道受到控制， 通过晚第三纪（阿尔卑斯山脉）的断裂和断层面， 明确表示，这一举措是“晚” 埋葬起源 这项研究的结果可以揭示新的作用， 深层循环的地下流体 碳酸盐岩，特别是那些作为石油，天然气， 和热液矿石。

The origin of massive replacement dolomite remains one of the major unresolved problems of sedimentology. Presently favored interpretations for the origin of massive dolomites have centered on "early" low temperature processes involving surface or near- surface waters, and alternative processes such as "late" burial dolomitization have been overlooked by all but a few workers. The recent development of theoretical and computer models of groundwater flow systems in sedimentary basins makes the time ripe for a new look at burial dolomitization. Fluid flow is the one new factor of major significance that needs to be added to our attempts to resolve the dolomite problem. This is a study of the dolomite of the Jurassic Vajont Oolite of the Venetian Alps in northern Italy where preliminary field and geochemical work indicates that dolomitization occurred at elevated temperatures under burial conditions. The approach will be to integrate fieldwork, petrography, isotope and fluid inclusion data, and hydrologic modeling. The Vajont Oolite offers several special features that make such a study worthwhile: (1) it is massively but not completely dolomitized so that dolomitization fronts that give direct clues to the subsurface pathways of the dolomitizing fluids can be mapped (see Newton, Hardie and Phillips, 1990); (2) it consists of shallow water ooids that were resedimented in deep water by slope processes before alteration, thus shallow water dolomitization processes are ruled out; (3) the ooids and their intergranular cements are well preserved in the undolomitized parts of the Vajont sot hat it is possible to document in detail their pre-dolomitization petrography and isotope geochemistry; thus, the changes produced by dolomitization can be identified and measured; (4) exposures of partly but massively dolomitized Vajont in roadcuts reveal that dolomitization fluid pathways were controlled by fracture and fault planes of Late Tertiary age (Alpine orogeny), indication unequivocally that the dolomitization was of "late" burial origin. The results of the study could shed new light on the role of deeply circulated subsurface fluids in the origin of massive dolomites, particularly those that act as reservoirs to oil, gas, and hydrothermal ores.