Karl-Christoph Taupitz, 1967. "Textures in Some Stratiform Lead-Zinc Deposits", Genesis of Stratiform Lead-Zinc-Barite-Fluorite Deposits (Mississippi Valley Type Deposits), J.S. Brown
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The various textures observed are described and genetically interpreted on the basis of examples from the eastern Calcareous Alps (Kalkalps), from the German Muschelkalk. and from the Schiefergebirge (the Slate Mountains) of the German Rhineland.
In the eastern Alps and in Wiesloch sedimentary ore is found in almost every deposit; this occurs associated with dolomite-rich tuffaceous layers or in some such interruption of the normal lime sedimentation, generally apparent in the deeper parts of the old sea floor. Especially noteworthy are sedimentary breccias which also contain ore fragments; alternating deposits of ore and rock; and transgressions of younger limestone beds over older ore sediments with partial reworking of the ore. Early diagenetic ore deposits are not unusual and are not always easy to differentiate from sedimentary ore deposits, especially if they are associated with dolomitization and concretions. Completely different from these are hydatogenetic ores, occurring mainly in tectonic crevices or solution cavities or as impregnations or. metasomatically (i.e., as replacements), mainly in conjunction with a tectonic episode. In the Rhenish Schiefergebirge the older ore phase should be grouped with the magmatic lead-zinc veins, whereas in the Alps and in Wiesloch ore origin is a question of redeposition by deep waters. Above all. in the Alps. signs of solution in the older sedimentary ores are not infrequent. Unique in the Rhenish Schiefergebirge are the Karst solution cavities bearing sulfidic Fe, Zn, and Pb ores, plus barite and bituminous clays, in place of the normal paragenesis of Mn and Fe oxides and brightly colored clays. Ores in younger cave sediments also occasionally are found in the Alps.
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Genesis of Stratiform Lead-Zinc-Barite-Fluorite Deposits (Mississippi Valley Type Deposits)
Proponents of syngenetic theory base their interpretation largely on widespread uniform mineralization within a restricted stratigraphic interval and a consistent relationship of mineralization to sedimentary features. Proponents of epigenetic theory base their interpretation on mineralization of post-depositional structures, changes in extent and grade of ore, open space filling, district-wide lack of close control by sedimentary features, and relation of ore to tectonic structures. These and other criteria are evaluated in an attempt to define diagnostic criteria.
On the basis of the criteria defined the major lead-zinc deposits of Mid-continent United States must be considered as epigenetic.
Features of the Southeast Missouri lead district are listed. The deposits are epigenetic. The metals are believed to have been derived from nearby sedimentary basins and carried out of basins onto shelf areas in a concentrated brine. Movement of solutions was controlled by basement topography and deposition of metals occurred when solutions entered the Bonneterre formation on the flanks of and over buried knobs.
Objective.—The problem of origin of stratiform ore bodies cannot be resolved until we define, and agree upon, what constitutes diagnostic evidence for each type of deposit. This paper is an attempt to review the nature of geologic evidence; to define those features that must be regarded as unique and necessary criteria in classifying any deposit or district; and to apply the criteria to a major district, the Southeast Missouri lead deposits.
Theories of Origin.—The major elements of theories on origin of stratiform ore bodies are summarized in Table 1. A deposit is Syngcnetic if formed by processes similar to and simultaneously with the enclosing rock; epigenetic if introduced into a pre-existing rock (3). A diagenetic origin implies deposition of metals with the host sediments but with recrystallization, rearrangement, and limited migration.
The search for an acceptable theory of origin must be separated into its two component parts: (1) definition of whether the deposit has syngenetic, diagenetic, or epigenetic features and. (2) history of mineralization to explain source, transport, and deposition of metals. A statement of preferred hypothesis is meaningless until the first is answered and accounts for all geologic facts. The answer must be based solely on observed megascopic and microscopic features and on geochemical and isotopic data; it should not be biased by lack of knowledge to answer all phases of the second. In evaluating the evidence to determine type of deposit one cannot be concerned