Travertine lithofacies types and their springs water composition in the Garab area, south Mashhad

The quaternary to recent travertines of Garab spring systems is located between Binaloud mountains and Mashhad plain, in northeast of Iran. The Binaloud zone contains of Paleo- Tethys remnants including diorite, meta- flysch, meta- ophiolite and granodiorite. This area is affected by extensional fault system of Sangbast- Shandiz and travertines have been formed in southeast of this fault and related fractures. Based on morphological data, field and petrography observations, there are two main systems of old (inactive) and recent (active) deposits within various lithofacies. These are crystalline crust, carbonate black mud, rafts, foams, shrubs and lamination. They are formed due to precipitation of calcite and aragonite polymorphs as the main mineralization phases that confirmed by XRD analysis. These deposits have high Fe contents based on ICP-OES analysis as iron oxide (hematite) that present within pores and laminations with brown to orange color. Plants are also played a main role in precipitation of this type of carbonate. In the Garab area, there are several evidences of travertine precipitation in form of ice calcite on plants stems that grow in spring margins or woody fragments in water. Plants with photosynthesis mechanism produce the chains of oxygen bubbles that covered by carbonate in the next stages. In some wall successions there are some evidence of erosional surface with karstic features. The travertine deposits are also affected by extensive diagenetic process with saturation fluid circulations. There are seven springs in the Garab area with primary origin of surface water due to rainfall. The springs water contain high concentration of dissolved ions such as Ca2+, Mg2+, HCO3 -, SO42-, Cl- and Na+ that can be related to dissolved salty soils or present of evaporates and calcium carbonates. The presence of halite cubic crystals have confirmed by Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) analysis. Using hydrochemical diagrams for spring systems show the same type water of Na- Cl and Ca- HCO3- SO4 composition for all springs that indicating a subsurface relation between these seven springs. Similar lithofacies have been recorded at Pamukkale in Turkey, Mammoth hot springs, Yellowstone National Park in USA and Euboea Island in Greece.