A Study of the Origin and Significance of Pyrite Ooids

小行星9706178 黄铁矿卵状体是一种直径达4毫米的沉积颗粒，显示出围绕着成分可变的核的同心黄铁矿纹层。 Hayes（1915）首次提到了这种颗粒，此后文献中偶尔提及（例如Kalliokoski，1966; Gorter，1991; Taylor，1949; Kearsley，1989）。 在所有这些参考文献中，发现黄铁矿类鲕粒与鲕粒铁矿石共生，用几句话概括地描述，并解释为碎屑岩或针铁矿类鲕粒的成岩蚀变。 Hayes（1915）和Carozzi（1972）是认为黄铁矿类鲕粒为原生成因的唯一例外。 我对黄铁矿类软泥的兴趣源于我第一次在田纳西州的查塔努加页岩中遇到这些神秘的颗粒。 在一个沉积序列中，该序列被认为是在缺氧条件下在相对较深的水中沉积的（Potter等人，1982; Ettensohn等人，1988; Woodrow等人，1988; Leventhal等人，1987年），这些颗粒，与他们的搅拌和波改造的含义，似乎是奇怪的地方。 从那时起，我开始意识到其他黄铁矿类卵的出现，并能够从其中两个中获得材料。 用岩相学和电子显微镜（反射/透射光; SEM和BEI模式; EDAX）检查了来自查塔努加页岩、德科拉页岩（爱荷华州寒武纪）和Powers Steps地层（纽芬兰奥陶纪Wabana铁矿）的样品和抛光薄片。 这项初步研究表明，黄铁矿卵可能确实是主要的盆内颗粒的功能，也表明，有几种类型的黄铁矿卵可能是反映古海洋条件的沉积时间。 请求提供资金，对不同沉积环境和时期的黄铁矿类卵进行详细的比较研究。 研究的目的是：（1）证实原生黄铁矿类卵确实存在;（2）表明原生黄铁矿类卵是一种比通常认识的更为普遍的现象;（3）确定其形成条件;（4）了解黄铁矿类卵形成的各种途径;（5）获得有关古海洋学参数的信息，如缺氧的存在或不存在，环境的能量水平、水深、海底和表层沉积物的化学条件以及沉积速率。

9706178 Schieber Pyrite ooids are sedimentary grains of up to 4mm diameter that show concentric pyrite laminae around a core of variable composition. First mention of such grains was made by Hayes (1915), and since then they have sporadically been mentioned in the literature (e.g. Kalliokoski, 1966; Gorter, 1991; Taylor, 1949; Kearsley, 1989). In all these references, pyrite ooids are found in association with oolitic ironstones, are summarily described in a few sentences, and interpreted as diagenetic alterations of chamositic or goethitic ooids. Hayes (1915) and Carozzi (1972) are the lone exceptions in considering pyrite ooids as of primary origin. My interest in pyrite ooids stems from my first encounter with these enigmatic grains in the Chattanooga Shale of Tennessee. In a sedimentary sequence that was supposedly deposited under anoxic conditions in comparatively deep water (Potter et al., 1982; Ettensohn et al., 1988; Woodrow et al., 1988; Leventhal et al., 1987), these grains, with their implication of agitation and wave reworking, seemed to be oddly out of place. Since then I have become aware of other occurrences of pyrite ooids, and was able to acquire material from two of them. Samples and polished thin sections from the Chattanooga Shale, the Decorah Shale (Cambrian of Iowa), and the Powers Steps Formation (Wabana iron ores, Ordovician of Newfoundland) were examined with petrographic and electron microscopes (reflected/transmitted light; SEM and BEI mode; EDAX). This preliminary study showed features that suggest that pyrite ooids may indeed be primary intrabasinal grains, and also indicates that there are several types of pyrite ooids that may well be reflective of paleoceanographic conditions at the time of deposition. Funds are requested for a detailed comparative study of pyrite ooids from a variety of depositional settings and time periods. The aim of the study is (1) to verify that primary pyrite ooids do indeed exist, (2) to show that primary pyrite ooids ar e a more widespread phenomenon than typically appreciated, (3) to determine the conditions for their formation, (4) to understand the various pathways for pyrite ooid formation, and (5) to derive information about paleoceanographic parameters, such as presence or absence of anoxia, energy level of the environment, water depth, chemical conditions at the seafloor and in the surface sediment, and rate of deposition.