The results on numerical physico-chemical modeling of interaction in water-rock system on the example of Oxfordian horizon Yu₁ of the northern regons of Novosibirsk oblast are presented for the first time. It has been established that, there is practically no equilibrium with primary (endogenous) minerals anorthite, albite, and microcline, despite the low salinity of groundwater (up to 46 g/dm3) and their long interaction with rocks (tens, and possibly hundreds of millions of years). At the same time, groundwater is in equilibrium with mica minerals, Ca-, Na- and Mg- montmorillonites, kaolinite, Mg-chlorite. A carbonate barrier always acts on the path to establishing equilibrium of groundwater with primary aluminosilicate minerals. Petrographic studies of silty-sandy rocks established the genetic series of authigenic minerals of diagenesis and catagenesis. Relict diagenetic minerals are represented by glauconite, pyrite, siderite, first-generation calcite, kaolinite, anatase and leukoxene. Among catagenetic minerals predominates calcite of the second and third generation predominates, quartz, kaolinite are less developed, and siderite, chlorite, zeolites, albite, and dolomite are slightly developed. The results of petrographic studies confirm the thermodynamic calculations.