--> Abstract: Model for Trace-Element Partitioning in Limestones, by Nicholas E. Pingitore, Jr.; #90961 (1978).
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Abstract: Model for Previous HitTraceNext Hit-Element Partitioning in Limestones

Nicholas E. Pingitore, Jr.

The partitioning of strontium and magnesium into calcite (kSrcalcite = 0.14; kMecalcite = 0.05, under diagenetic conditions) yields important insight into diagenetic processes in limestones. Other Previous HittraceNext Hit elements, such as zinc and manganese, exhibit different behavior, for their partition coefficients are greater than unity (kZncalcite = 5.5; kMncalcite = 15). Integration of information from the distributions of zinc and manganese with that from strontium and magnesium requires a general model of Previous HittraceNext Hit-element behavior. The parameters of distribution coefficient, water flow Previous HitrelativeNext Hit to reaction rate (openness of chemical system), and water chemistry before entering the diagenetic site normally determine the enrichment or depletio in Previous HittraceNext Hit element of calcite Previous HitrelativeNext Hit to the parent aragonite (or calcite). Four distinct situations ensue. (1) Autodepletion is preferential loss of Previous HittraceNext Hit element from the diagenetic site due to high water flow Previous HitrelativeNext Hit to precipitation rate and k<1. Calcite depleted in Previous HittraceNext Hit element Previous HitrelativeNext Hit to the parent aragonite results. (2) Autoenrichment is enrichment of the calcite in Previous HittraceNext Hit element when k>1. (3) Alloenrichment is precipitation from a liquid enriched in Previous HittraceNext Hit element (Previous HitrelativeNext Hit to the parent aragonite) before it enters the diagenetic site; the enrichment of the liquid required increases with decreasing k. (4) Allodepletion occurs when a liquid rich in calcium and poor in Previous HittraceNext Hit element flushes through the diagenetic site. If k~1, each liquid cycle may introduce sufficient calc um that, after the liquid dissolves aragonite, its Previous HittraceTop element/calcium ratio remains less than that of aragonite, yielding a depleted calcite.

AAPG Search and Discovery Article #90961©1978 AAPG Annual Convention and Exhibition, Oklahoma City, Oklahoma