How to determine the compositional maturity and structural maturity of sandstones and their genetic significance
Gravel clastic sediments: rock conglomerate + quartzite gravel / other rock gravels;Clastic sediments of sand or silt: single crystal quartz / single crystal feldspar; single crystal quartz + flint cuttings;Mud clastic sediments: Al2O3 / Na2O (two chemical analysis results);Detrital composition maturity reflect geological clastic components through time and strength, they are affected by climate and tectonic conditions are largely restricted. Generally, immature sandstone is near provenance deposits, containing many unstable clastic rock debris, such as feldspar and mafic minerals. The high maturity of the sandstone is after a long distance transportation, products suffered transformation, almost all are composed of quartz sandstone types. Therefore, in the presence of debris and detrital minerals and relative abundance, namely composition maturity, is reflect the geological conditions, source area weathering degree and moving distance.Structural maturity refers to the extent to which the clastic material is close to the ultimate structural characteristics under the transformation of weathering, transport and sedimentation, and is usually expressed as the base content, the ratio of sand to mud or the ratio of the particles to the matrix
The sandstone in sorting and psephicity and matrix content influences the structure maturity, generally increases with the increase of the times and then handling transport distance. The sandstone structure maturity and compositional maturity usually two line can also be inconsistent. The structure of the most mature sandstone in containing clay matrix, debris the particles should also have good sorting and circular degree. These characteristics reflect the sediments undergo full flow jigging and abrasion.
We usually say that the degree of maturity is generally relative to the sandstone is divided into structural maturity and compositional maturity of two;Composition maturity: refers to the sandstone clastic components close to the ultimate product of the most stable in the transformation of weathering and transportation and sedimentation under the degree (degree of maturity and the relative content of the most stable components in clastic rocks to mark their composition, usually with stable components) and unstable component content or the ratio of to express.In the study of sandstone, quartz and feldspar and other commonly used ratio of cuttings as a measure indicator of maturity. In the light components, non single crystal quartz wave is the most stable, the relative content of it is an important sign of maturity of clastic rocks, the heavy mineral, tourmaline, zircon (Zircon), (Tourmaline) Jin Hongshi (Rutile) is the most stable, the proportion of the three minerals for transparent heavy minerals called "ZTR" index, is indication of compositional maturity.
