ALBERT

Description: Despite the presence of known economic resources in Canada's Arctic archipelago, Victoria Island remains understudied. This study addresses the fluid history and economic potential of two major carbonate units on Victoria Island by integrating fluid inclusion microthermometry with SEM-EDS analysis of evaporate mounds. Three cements containing fluid inclusion assemblages (FIA) occur in the Neoproterozoic Wynniatt Formation: saddle dolomite, brown dolomite and calcite, in paragenetic order. The two dolomite-hosted cements have average homogenisation temperatures ( T h ) for FIAs ( n  = 3) of 108°C (saddle) and 101 and 116°C, but metastability precluded determining salinities; most calcite-hosted fluid inclusions are too small and/or necked to obtain T h values, but rare larger inclusions have salinities from 1.7 to 0.4 wt. % NaCl equiv. SEM-EDS analysis of evaporate mounds indicates the fluid changed from an early K-rich (saddle dolomite), to a later K + Na (brown dolomite), and finally Na-rich (calcite), which suggests mixing of two end-member fluids (i.e. Na-rich and K-rich). Dolostone of the lower Paleozoic ‘Victoria Island formation’ contains two cements: early quartz and late dolomite. Quartz-hosted FIAs ( n  = 2) have an average T h value of 126°C, and salinity of 23.2 wt. % NaCl equiv., whereas FIAs ( n  = 3) in dolomite have average T h values of 109, 116 and 124°C; metastability precluded determining salinity. Evaporate mound analysis for the cements indicates evolution from a Na-rich to a Na + K fluid through interaction with reservoir rocks. A reduced, metal-rich fluid was present during quartz precipitation, as implied by the presence of pyrite framboids along growth zones and nanoparticles of barite and sulphide minerals (Zn, Cu and Pb) in evacuated inclusions, which suggests the area may have potential to host base-metal mineralisation. Importantly, distinguishing different fluid compositions in both of the case studies would not have been possible without evaporate mound analysis and therefore the results emphasise integrating this technique into diagenetic studies. Diagenetic fluids for two major carbonate units on Victoria Island have compositions that indicate mixing of multiple fluids and/or interaction with reservoir rocks. The utility of integrating the SEM-EDS analysis on evaporate mounds is demonstrated to be effective in characterising fluid chemistry beyond standard microthermometry methods, particularly with metastable or small fluid inclusions. Metal-rich fluids were present during cement precipitation, as indicated by nanoparticles in evacuated fluid inclusions, and therefore the possibility of economic potential exists in this area.

Description: We provide a case study prioritizing instream flow restoration activities by sub-basin according to the habitat needs of Endangered Species Act (ESA)-listed salmonids relative to climate change in the central Columbia River basin in Washington State (USA). The objective is to employ scenario analysis to inform and improve existing instream flow restoration projects. We assess the sensitivity of late summer (July, August and September) flows to the following scenario simulations – singly or in combination: climate change, changes in the quantity of water used for irrigation and possible changes to existing water resource policy. Flows for four sub-basins were modeled using the Water Evaluation and Planning system (WEAP) under historical and projected conditions of 2020 and 2040 for each scenario. Results indicate the Yakima will be the most flow-limited sub-basin with average reductions in streamflow of 41% under climate conditions of 2020 and 56% under 2040 conditions; 1.3-2.5 times greater than those of other sub-basins. Additionally, irrigation plays a key role in the hydrology of the Yakima sub-basin – with flow reductions ranging from 78% to 90% under severe to extreme (i.e., 20-40%) increases in agricultural water use (2.0-4.4 times the reductions in the other sub-basins). The Yakima and Okanogan sub-basins are the most responsive to simulations of flow-bolstering policy change (providing salmon with first priority water allocation and at biologically-relevant flows), as demonstrated by 91-100% target flows attained. The Wenatchee and Methow sub-basins do not exhibit similar responsiveness to simulated policy changes. Considering climate change only, we conclude that flow restoration should be prioritized first in the Yakima and Wenatchee sub-basins, and second in the Okanogan and Methow. Considering both climate change and possible policy changes, we recommend that the Yakima sub-basin receive the highest priority for flow restoration activities to sustain critical instream habitat for ESA-listed salmonids.