<![CDATA[This study evaluates the potential contribution of differential thermal contraction between quartz and feldspars to secondary porosity generation during cooling of quartz-bearing crystalline rocks. We reassess and extend the thermomechanical framework proposed by Rossello and Gallardo (2026) by integrating its quantitative model with published thermal-expansion data and experimental evidence for thermally induced microfracturing in granite. The model predicts theoretical thermally induced porosity of approximately 0.4–1.2%, depending mainly on quartz abundance and the contrasting thermal behaviour of quartz and feldspars. The β→α quartz transition at approximately 573–575 °C at atmospheric pressure produces a marked change in the thermal and elastic behaviour of quartz and may contribute to differential strain and damage within the crystalline framework. However, experimental studies demonstrate that thermal microcracking begins over a broader temperature range, commonly before the quartz transition, and may subsequently propagate and coalesce during thermal evolution. The calculated porosity therefore represents potential secondary pore space rather than directly measured effective reservoir porosity. Its reservoir significance depends on subsequent tectonic deformation, fluid circulation, fracture reactivation, and preservation of fracture connectivity. The results support differential thermal contraction, including the β→α quartz transition, as a potentially significant contributor to the initial development of secondary porosity in quartz-bearing crystalline rocks and provide a testable framework for evaluating fractured basement hydrocarbon reservoirs.]]>
