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Journal Article

# Chemical Zoning in Garnets from Rocks around the Massive Sulfide Deposits at Ducktown, Tennessee, and Its Implications

Sunit Kumar Addy and Peter J. M. Ypma
The Journal of Geology
Vol. 86, No. 3 (May, 1978), pp. 385-392
Stable URL: http://www.jstor.org/stable/30061990
Page Count: 8
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## Abstract

Garnets from the alteration zones and the country rocks surrounding the massive sulfide deposits at Ducktown, Tennessee, show strong compositional zoning of Mn and Fe and occasionally that of Ca and Mg. Observed continuous decrease of Mn (and Ca) and continuous increase of Fe (and Mg) from the core to the edge of crystals indicate that the mineral has been formed during prograde metamorphic events. Previous study shows that the minerals in the alteration zones, including garnet, are depleted in their $\delta^{18}O$ values by approximately 2 per mil compared to the country rocks. Since the compositional zoning of garnet indicates no recrystallization at a later time, it is concluded that garnets in the alteration zones were developed during the regional metamorphism in contact with an isotopically lighter hydrothermal solution which influenced the rocks surrounding the ore body. The study does not favor a post-metamorphic emplacement of the sulfides and the subsequent formation of the alteration zones.

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