The existing hypotheses of giant evaporites formation were mostly formulated prior to the establishment of the plate tectonics theory. With little knowledge on the lithosphere’s varying thermal states, especially during past tectonic events, the most intuitive mechanism for producing large salt deposits was considered to be solar evaporation of seawater. However, large volumes of salts (mostly chlorides and sulphates) have been discovered both on and deep below Earth's surface, where large salt accumulations formed in deep marine basins are particularly difficult to explain with the surface evaporation model. Here, we re-address this important problem by analyzing the spatio-temporal distribution of evaporites from 128 evaporitic basins over the globe. We found that throughout the Phanerozoic, LEPs (Large Evaporite Provinces) occurred in mostly salt-bearing basins, with a strong affinity to active tectonic deformation. We show that the volumes of evaporites and the frequency of evaporate formations synergistically correlate with tectonic activities and large igneous provinces (LIPs). In contrast, both LEPs and LIPs formed consistently earlier than and have a poorer correlation with climate factors (sea surface temperature and CO2 content), implying that solar energy and evaporation played a secondary role in LEP formation. Given that the deep-circulating hydrothermal system, where LEP formed, is ultimately driven by tectonic heat input from the Earth’s interior, we propose that enhanced geothermal gradients of the lithosphere can better explain the location, timing, and amounts of salt deposits than the traditional solar evaporation hypothesis. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Published Online: June 12, 2023; https://doi.org/10.59717/j.xinn-geo.2023.100008. Citation: Qin Z., Tang C., Liu L., et al., (2023). Large evaporite provinces: Warming from above or heating from below?. The Innovation Geoscience 1(1), 100008.
Figure 1. Models of the formation of LEPs controlled by geothermal energy in different geologic settings, volumes of reconstructed evaporites and LEPs, and areas and numbers of LIPs at different geologic times. (A) Plot of the formation age vs. The volume for the reconstructed evaporites and LEPs formed during the Phanerozoic (1–Mediterranean, 2–Red Sea, 3–South Atlantic, 4–Gulf of Mexico, 5–Northern Sahara, 6–Eastern European, 7–Iran-Pakistan, 8–East Siberian). (B) Plot of the area vs. the age for the LIPs formed during the Phanerozoic; the pink boxes indicate LIPs without area data. The orange bars represent six periods of occurrence of LEPs during the Phanerozoic. Link to dataset: https://www.scidb.cn/s/AFr6vm, and the DOI is 10.57760/sciencedb.08249
|
