Factors controlling the geometry of travertine mounds: Insights from Heinitang (China)

Abstract

Travertine mounds are common spring-constructed landforms with highly variable geometries, but factors controlling their development have not yet been fully understood. To investigate processes linked with their lateral and vertical growth, this study investigated travertine mounds at Heinitang (China) and compared them with typical mounds around the world. Calcium concentration variation modelling and height evaluation of travertine mounds were also performed. The lateral extent of travertine mounds was found to be mainly controlled by Ca 2+ and HCO À 3 concentrations and water discharge: relatively small metre-scale mounds, like those from Heinitang, are largely the products of Ca 2+ -deficiency (<150 mg L −1 , commonly <100 mg L −1 ) or HCO À 3 -deficiency (<500 mg L −1 ) springs with low discharges (<0.1 L s −1 ), whereas springs with higher Ca 2+ and HCO À 3 concentrations and discharges give rise to the formation of wider mounds. Additional factors affecting mound lateral development include infiltration, evaporation, micro-organisms, water cooling, CO 2 degassing and flow paths. Height of travertine mounds cannot be simply considered to represent the piezometric surface, because the vertical growth of travertine mounds is also influenced by the water table change triggered by tectonic pulses and climate fluctuations, and the closing of conduits induced by self-sealing. The extinction of travertine mounds at Heinitang is, for example, probably caused by the water table lowering triggered by earthquakes or climate drying after 4 kyr BP. These findings offer new inputs for the better understanding of factors controlling travertine mound development and might assist in the reconstruction of fluid properties, hydrodynamics, tectonics and climate fluctuations in fossil geothermal systems with travertine mounds.

Travertine depositional systems of Central Italy: Rapolano Terme and the Acque Albule Basin. An overview of geometries and lithofacies associations of the depositional setting

“…2C). The proximal zone is the area where thermal water flows out from a spring, starts the deposition of calcium carbonate deposits, forming fissure-ridge, mound, pinnacle and mud pot macro-morphologies (Curewitz and Karson, 1997;Brogi et al, 2021;Luo et al, 2022b). The intermediate zone is the area where thermal water, flowing towards lower depositional areas, forms different inclined geometries as slope and channel (Mancini et al, 2019a).…”

Travertine mineralogical characteristics and development level in Huanglong, a world natural heritage, china：derived from late pleistocene to early holocene glacial u-shaped valley carbonate deposits

“…Okumura et al (2013) proposed that algae metabolism EPS(extracellular secretion) has a regulatory effect on the microscopic morphology and arrangement of travertine crystals. Sun et al (2022) summarized the distribution and sedimentary types of travertine in the Qinghai-Tibet Plateau; Gao et al (2013) discovered oolitic travertine mantle particles in Huanglong Scenic area and interpreted their mineralogy by means of characterization; Luo et al (2022) summarized the effects of different organisms on the pore and crystal structure of travertine.…”