Abstract

Emission spectrography has been used to study distribution of trace elements in Paleozoic limestones surrounding Pb-Zn ore bodies near Santa Rita, New Mexico, and subsequent transportation of these traces into overlying Tertiary beds. Analyses are given for Pb, Zn, Cu, Ag, and V, important ore metals, and Mn and Al, prominent in pre-ore silication.

Pb highs from Tertiary fault zones may be correlated with ore bodies in pre-Tertiary rocks, but Zn has been leached unless considerable gouge is present. Pb and Zn highs from a remote part of the Tertiary area encourage further exploration.

A zoning of traces occurs in Tertiary mont-morillonite zones bordering the ore-localizing Groundhog fault. Near a producing mine, Ag wa deposited for 20 feet from the fault, and Pb for 40 feet. Most Zn highs are in a 60-foot zone, but a few extend as much as 250 feet.

In limestones around Pb-Zn ore bodies, trace-element distribution is controlled by small fractures, and penetration into massive wall-rock is negligible. Zn highs occur close to ore bodies, and Pb highs farther away. The shape of the Pb gradient seems controlled largely by temperature, and the relative importance of pre-ore silication and ore-deposition may be important here.

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