Telogenetics, part of Diagenetic english version

telogenetic process of diagenetic

1. Defenition Telogenesis is late stages diagenesis that accompanies or follow uplift of previously buried sediment into the regime of meteoric waters Sediment that are still deeply buried in sedimentary basins (never uplifted) have not undergone telogenesis Uplift and expossure of the sediment pile brings sediment into telogenetic regime, characterized by lowered pressures and temperaturesand by generally oxidizing, meteoric pore waters Mineral assemblages formed under hight temperatures and pressures during mesogenesis tend to become unstable under the changed conditions of telogenesis

2. Exposure of sedimentary rocks above base level by tectonic uplift ( telogenesis ) or sea-level fall exposes them to atmospheric processes and physical erosion and chemical weathering. Meteoric (fresh, dilute) waters can penetrate deeply into exposed or tectonically uplifted sedimentary rocks through permeable units or fracture porosity and develop extensive karst and dissolution features in carbonate-dominated successions

3. Telogenesis Process and Mechasnism After folding and faulting, denudation and partial truncation and uplifting of a sedimentary sequence, can bring s e diments again to the surface. Hydraulic heads of meteoric water are formed and sediment bodies are recharged and flushed with meteoric water, causing a state of disequilibrium. Flow rates of interstitial fluids increase, since permeability and porosity increase through relaxation of the rock. After a long burial diagenesis or in case of an initially marine mineralogy, minerals will not be in equilibrium with surface conditions. Also , diagenesis is controlled by the porosity and permeability patterns in the s ediment

4. Telogenesis modifications include dissolution of previously fored cements or framework grains (creating porosity), or in situ alteration of framework grains to clay minerals (occluding porosity) Depending upon the nature of pore waters, silica or carbonate cements can be precipitated E.g., carbonate cements precipitates in the vadose zone by evaporative pumping under climatic conditions that favor evaporation.

5. Diagenetic changes include, oxidation and destruction of organic matter, oxidation of iron carbonates to form iron oxides and eventually hematite, oxidation of sulfides to form sulfates such as gypsum, dissolution of pyroxenes, amphiboles, and other heavy minerals during weathering, and alteration of detrital feldspar to kaolinite. Detrital feldspar are also reported to alter to illite and authigenic K-feldspar Other telogenetic changes may include alteration of chlorite to vermiculite and dissolution of iron oxides and carbonates

6. Sediment Rock on Telogenesis Limestone Dolomit Sandstone