The Red Chris porphyry Cu-Au deposit is located in the Stikinia island-arc terrane in northwest British Columbia. It is hosted by the Red Stock, which has five phases of porphyry intrusions: P1, P2E, P2I, P2L, and P3. New U-Pb dating of zircon shows that these intrusions were emplaced over a ~10 m.y. period, with P1 intruded at 211.6 ± 1.3 Ma (MSWD = 0.85), P2I at 206.0 ± 1.2 Ma (MSWD = 1.5), P2L at 203.6 ± 1.8 Ma (MSWD = 1.5), and P3 at 201.7 ± 1.2 Ma (MSWD = 1.05). The ore-forming event at Red Chris was a short-lived event at 206.1 ± 0.5 Ma (MSWD = 0.96; weighted average age of three Re-Os molybdenite analyses), implying a duration of 0.4), indicating that their associated magmas were moderately oxidized. The magmatic water contents estimated from plagioclase and amphibole compositions suggest H₂O contents of ~5 wt %. Taken together, the P1 to P3 porphyries are interpreted to be moderately oxidized and hydrous. The porphyry phases are differentiated by sulfur and chlorine contents. The SO₃ contents of igneous apatite microphenocrysts from the mineralization-related P2 porphyries are higher (P2E: 0.28 ± 0.10 wt %, n = 19; P2I: 0.32 ± 0.17, n = 15; P2L: 0.29 ± 0.18 wt %, n = 100) than those from the premineralization P1 (0.11 ± 0.03 wt %, n = 34) and postmineralization P3 porphyries (0.03 ± 0.01 wt %, n = 13). The chlorine contents in apatite grains from the P2E, P2I, and P2L porphyries are 1.47 ± 0.22 (n = 19), 0.82 ± 0.10 (n = 15), and 1.47 ± 0.28 wt % (n = 100), also higher than those from P1 (0.51 ± 0.3 wt % Cl, n = 34) and P3 (0.02 ± 0.02 wt % Cl, n = 17). These results imply that the sulfur and chlorine contents of the P2 magmas were higher than in the P1 and P3 magmas, suggesting that elevated magmatic S-Cl contents in the P2 porphyries may have been important for ore formation. Although the process that caused the increase in sulfur and chlorine is not clear, reverse zoning seen in plagioclase phenocrysts from the P2 porphyry, and the occurrence of more mafic compositions in P2L, suggest that recharge of the deeper magma chamber by a relatively S-Cl-rich mafic magma may have triggered the ore-forming hydrothermal event.

We present a new approach to laser ablation inductively coupled plasma mass spectrometry (LA‐ICP‐MS) U‐Pb dating of carbonates based on selection and pooling of pixels from 2‐D elemental and isotopic ratio maps. This image mapping technique is particularly useful for targeting subdomains in samples with complex geological histories. Key major and trace elements that are sensitive to detrital components, postformational fluid ingress, mineralogical changes, or diagenetic overprinting are measured along with the Pb and U isotopic data. Laser sampling is undertaken along successive linear rasters that are compiled into maps using the Monocle add‐on for Iolite, with one pixel in the map corresponding to one time slice of the time‐resolved signal. These element, element ratio, and isotope ratio maps can be overlain over photomicrographs or scanning electron microscopy images to spatially link compositional data to textural and structural features. The pixels corresponding to likely homogeneous age domains can be isolated by applying appropriate selection criteria (e.g., Th < 0.3 ppm, Mg/Ca < 0.004) and pooled into pseudo‐analyses using a proxy for the parent/daughter ratio (e.g., ²⁰⁷Pb/²³⁵U, ²³⁸U/²⁰⁸Pb) to retrieve the largest possible spread of the data points on isochron diagrams. The approach is best suited for analytical setups capable of rapidly or simultaneously scanning over a large mass range and can yield a precision of ±1% or better on quadrupole instruments depending on U concentration, ²³⁸U/²⁰⁴Pb, and age of the sample. The sample‐specific filtering criteria for selection and rejection of data and their rationale can be reported, resulting in more transparency with regard to data processing.

The ac Stark effect was used to induce resonant energy transfer between translationally cold ${}^{85}\mathrm{Rb}$ Rydberg atoms. When a 28.5 GHz dressing field was set at specific field strengths, the two-atom dipole-dipole process $43d_{5/2}+43d_{5/2}\to 45p_{3/2}+41f$ was dramatically enhanced, due to induced degeneracy of the initial and final states. This method for enhancing interactions is complementary to dc electric-field-induced resonant energy transfer, but has more flexibility due to the possibility of varying the applied frequency.