Significance of authigenic quartz euhedra after sulfates; example from the Lockport Formation (Middle Silurian) of New York
Significance of authigenic quartz euhedra after sulfates; example from the Lockport Formation (Middle Silurian) of New York
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DOI：
10.1306/212f7bda-2b24-11d7-8648000102c1865d
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发表时间：
1980-12
影响因子：
2
通讯作者：
G. Friedman;Vijai Shukla
中科院分区：
文献类型：
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作者：
G. Friedman;Vijai Shukla
摘要描述了纽约州西南部卡塔罗古斯县西南部洛克波特组(中志留统)一口井中的自生石英真面体。该组为白云岩，白云母部分为白云母，白云母产于组的上半部，是自生石英真面体的寄主，自生石英真面体孤立或聚集出现。孤立的真六面体呈等角形、棱柱形或板条形，表现出广泛的边界腐蚀和长度慢的光学特征。石英真面体的聚集体要么呈扇形，要么由四面体组成的簇状向四面体辐射。在这两种情况下，都可以看到腐蚀效应和长-慢光学特性。这些自生石英真面体被解释为硫酸盐晶体溶解所产生的填充空隙。导致这一解释的特征是石英晶体形态，石英真面体与碎屑石英的比较，以及石英和硫酸盐(石膏和天青石)的比较晶体形态。硫酸盐的沉淀一定发生在含有碎屑石英的石灰泥中。PH波动导致硫酸盐溶解和石英沉淀。白云石化作用导致了石英晶界的侵蚀。
ABSTRACT Authigenic quartz euhedra are described from a well drilled in the Lockport Formation (Middle Silurian) southwestern Cattaraugus county, southwestern New York State. The formation is dolostone part of which is dolomicrite; the latter, occurring in the top-half of the formation, is the host to authigenic quartz euhedra which occur isolated or in aggregates. Isolated euhedra are equant, prismatic, or lath shaped and display extensive boundary corrosion and length-slow optical character. Aggregates of quartz euhedra are either fan-shaped or clusters composed of euhedra radiating out in all directions. In both cases corrosion effects and length-slow optical character are seen. These authigenic quartz euhedra are interpreted as filling voids created by dissolution of sulfate crystals. Feat res leading to this interpretation are quartz crystal morphology, comparison of quartz euhedra with detrital quartz, and comparative crystal morphology of quartz and sulfates (gypsum and celestite). Precipitation of sulfates must have occurred in lime mud which contained detrital quartz. The pH fluctuations led to sulfate dissolution and quartz precipitation. Finally, dolomitization resulted in corrosion of quartz-crystal boundaries.