Th-Pb and U-Pb Dating of Ore-Stage Calcite and Paleozoic Fluid Flow

Abstract

ceptihility of Sr3CuPtc jIr,,j06 follolvs the predicted behavior of a random quantum spin chain (Figs. 3 and 4). A t high temperatures, the susceptibility has a linear x versus 1/T dependence and is Curie-like. In this regime, where there is 110 ordering among unpaired electrons, the spins act independently. A fit of the high-temperature data ga17e a Weiss constant of 8 = -12.7 K and a spin-only tnotnent of (I, = 2.11 Bohr magnetons. This moment is in excelle~lt agreement with that expected for a sample containing, on a17erage, one S = ?h Cu ion and o~le-half S = lh Ir ion, nhich should yield an effecti1.e moment of (I, = 2.12. A t lon.er temperatures, there is a t r a n sition to a regime where spin-spill interactions hecome important, as indicated by the broad cur17e in the inl~erse susceptibility. This transition marks the alignment of spins to form islands of effecti1.e spins, as discussed above. Comparison of Figs. 3 and 4 sho\vs that theory and experiment are in good agreement.

Paleomagnetic dating of Upper Mississippi Valley zinc–lead mineralisation, WI, USA

“…Note that the older deposits/districts are more distant from Appalachian -Ouachitan orogenic belt. Central Missouri (CM), 303 F 17 Ma, paleomagnetism, Symons and Sangster (1991); Central Tennessee (CT), 260 F 42 Ma, Th -Pb orestage calcite Brannon et al (1996a); 245 F 10 Ma, paleomagnetism, Lewchuk and Symons (1996); Northern Arkansas (NA), 265 F 20 Ma, paleomagnetism, Pan et al (1990); Old Lead Belt (OLB), 286 F 20 Ma, paleomagnetism, Wisniowiecki et al (1983); Tri-State (TS), 251 F 11 Ma, Th -Pb ore stage calcite, Brannon et al (1996a); Upper Mississippi Valley (UMV), 270 F 4 Ma 87 Rb -86 Sr sphalerite age, Brannon et al (1992Brannon et al ( , 1996b; 282 F 10 Ma, paleomagnetism, this study; Viburnum Trend (VT), southeast Missouri, 273 F 10 Ma, paleomagnetism, Symons et al (1998a). match the observed fluid inclusion temperatures on the south side of the UMV district, and possibly a second is an explanation for the occasional 185 -220 jC fluid inclusions found in the UMV.…”

Alpha thermochronology of carbonates

“…Sample 13496 is a dolomite-chalcopyrite-calcite MVT deposit from near Joplin, MO (Brannon et al, 1996). The Arrhenius relationship for calcite in Fig.…”

Timing and metal sources for carbonate-hosted Zn-Pb mineralization in the Franklinian Basin (North Greenland): Constraints from Rb-Sr and Pb isotopes

“…Further Rb-Sr dating of sphalerite may help to confirm and possibly extend the chronological story of hydrothermal base metal mineralization in the Franklinian Basin for a better understanding of their timing and genesis, which will be crucial to identify economic exploration targets. U-Pb dating attempts of ore-stage calcite (cf., Brannon et al, 1995Brannon et al, , 1996 could complement this but may be limited due to possible post-mineralization open-system behaviour.…”