Abstract:This article concerns application of cathodoluminescence~CL! spectroscopy to volcanic quartz and its utility in assessing variation in trace quantities of Ti within individual crystals. CL spectroscopy provides useful details of intragrain compositional variability and structure but generally limited quantitative information on element abundances. Microbeam analysis can provide such information but is time-consuming and costly, particularly if large numbers of analyses are required. To maximize advantages of both approaches, natural and synthetic quartz crystals were studied using high-resolution hyperspectral CL imaging~1.2-5.0 eV range! combined with analysis via laser ablation inductively coupled plasma mass spectrometry~LA-ICPMS!. Spectral intensities can be deconvolved into three principal contributions~1.93, 2.19, and 2.72 eV!, for which intensity of the latter peak was found to correlate directly with Ti concentration. Quantitative maps of Ti variation can be produced by calibration of the CL spectral data against relatively few analytical points. Such maps provide useful information concerning intragrain zoning or heterogeneity of Ti contents with the sensitivity of LA-ICPMS analysis and spatial resolution of electron microprobe analysis.

Silicate melt inclusions are ubiquitous in phenocrysts in porphyry copper deposits. Compared to melt inclusions in other igneous environments, those in porphyry copper deposits are more difficult to recognize and analyze, for a variety of reasons. The inclusions are usually partially to completely crystallized or altered by hydrothermal fluids, resulting in a dark, granular appearance. In this study, a protocol for identifying and homogenizing crystallized melt-inclusions from porphyry copper deposits is described. The protocol has been used to obtain preliminary data from melt inclusions in the Red Mountain, Arizona, and the Tyrone, New Mexico, porphyry copper deposits. Many melt inclusions in syn-and post-mineralization samples show evidence of alteration by magmatic-hydrothermal fluids that produced alteration and mineralization in the plutons, and many inclusions trapped crystals or fluid (or both) along with the melt. Elevated concentrations of metal in pre-mineralization (H 2 O-undersaturated) melt inclusions, and lower concentrations of metal in later syn-and post-mineralization (H 2 O-saturated) melt inclusions are consistent with models that invoke quantitative transfer of copper and other metals from the melt into the magmatic aqueous phase when the melt reaches H 2 O saturation. Results from Red Mountain and Tyrone are compared to melt inclusions from the White Island, New Zealand, active volcano.

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The use of resources from multiple habitats has been shown to be important to the production of aquatic consumers. To quantify the support of Great Lakes coastal wetland (WL) and nearshore (NS) habitats to yellow perch, we used otolith microchemistry to trace movements between the habitats. WL and NS water and fish samples were collected from lakes Huron and Michigan for water and otolith trace element analysis. Recently deposited otolith‐edge Sr : Ca and Ba : Ca from otoliths were strongly correlated with the chemistry of the water in which fish were caught. In general, Sr : Ca and Ba : Ca in otoliths were significantly greater for individuals collected from WL areas. Because of these observed chemical differences between WL and NS habitats, quadratic discriminant function analysis (QDFA) was used to classify individuals with high accuracy to the habitat from which they were collected. We then combined the predictive abilities of QDFA with the otolith chemistry transect data that represents an individuals' entire life, to classify habitat use through each fish's life. Our results suggest larval use of WL habitats as well as three life histories for adult yellow perch. These strategies include (1) fish utilizing WL once annually (2) WL residents (3) WL residence as juveniles followed by movement to nearshore as adults. This application represents a novel use of transect otolith microchemistry to reconstruct fish movements between freshwater environments across entire life spans at fine scales. These results suggest that regular movements of fish may facilitate the production of coastal fishes in the Great Lakes.