Geochemical mass balance studies

Geochemical mass balance studies (also known as input-output budgets) invoke a simple conservation-of-mass principle. If the flux of any element leaving a watershed (e.g., via streams), and the flux of that element into the watershed (e.g., via atmospheric precipitation) are known, the difference between the two can be calculated, and this difference must be due to the sum of all reactions and transformations involving that element which took place within the watershed. Pioneering mass balance studies on weathering profiles and/or small watersheds include those of Garrels and Mackenzie (,51, 52) and Cleaves and Bricker and their... 

Rates estimated in the above studies are shown in Table I. Watershed-scale geochemical mass balance studies yield calculated feldspar weathering rates one to three orders of magnitude slower than rates determined in laboratory experiments. 

Bulk rock chemistry of hydrothermally altered midoceanic ridge basalt has been well studied and used to estimate the geochemical mass balances of oceans today (Wolery and Sleep, 1976 Humphris and Thompson, 1978 Mottl, 1983). In contrast, very few analytical data on hydrothermally altered volcanic rocks that recently erupted at back-arc basins are available. However, a large number of analytical data have been accumulated on the hydrothermally altered Miocene volcanic rocks from the Green tuff region in the Japanese Islands which are inferred to have erupted in a back-arc tectonic setting (section 1.5.3). 

In this study, field, petrographic, bulk geochemical and mineral chemical data are presented with the aim of elucidating the mineralogical residence and spatial distribution of Ag within the HRMZ. A mass balance was calculated for Ag from electron microprobe analyses of sulfide minerals relative to bulk assays for the Main Zone deposit previously published by Wardrop (2006) for Sabina Silver Corporation. 

The water fluxes of the ECS are chiefly influenced by the Kuroshio surface water (KSW), the Kuroshio tropical water (KTW), and the Taiwan Strait water (TSW) entering into the ECS, and by the shelf surface water (SSW) leaving the ECS. The annual variation in concentration of DIP in these waters is small. If the geochemical cycle of phosphorus in the ECS is assumed to have reached a steady state, then the P budget of the ECS can be calculated using water and phosphorus mass-balance, using data obtained in previous studies. 

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