Work

Using Mg isotopes to constrain the formation temperature of dolomite

Year: 2025

Type: article

Abstract: The “dolomite problem” has long been a significant challenge in sedimentology, particularly regarding the determination of dolomite formation temperatures, a subject that remains highly debated. Magnesium (Mg) isotopes, due to their stability in dolomite during diagenesis and the strong relationship between isotopic equilibrium fractionation and temperature, present a promising tool for estimating the formation temperatures of dolomite. In this study, we analyzed the Mg isotope composition (δ 26 Mg) of various dolomite samples from the Ediacaran to Ordovician in the Tarim Basin, China, to assess the potential of Mg isotopes as a thermometer for dolomite formation. The δ 26 Mg values of micro-fine crystalline dolomites (D1) ranged from − 1.98 to − 1.69‰, fine-medium crystalline dolomites (D2) from − 1.68 to − 1.33‰, and medium-coarse crystalline dolomites (D3) from − 2.35 to − 1.99‰. Based on the Mg isotope temperature equilibrium fractionation equations, Δ 26 Mg dol−fluid = − 0.1554(± 0.0096) × 10 6 /T 2 or Δ 26 Mg dol−cal =0.1453(± 0.0106)×10 6 /T 2 , the calculated formation temperatures for D1 ranged from 45.0 to 65.4 °C, for D2 from 53.1 to 73.9 °C, and for D3 from 142.4 to 173.9 °C or 156.4 to 189.0 °C. These temperature estimates align closely with those derived from fluid inclusions and clumped isotopes in previous literature studies of the same formations, supporting the reliability of Mg isotopes as a method for determining dolomite formation temperatures. This study introduces an innovative approach for assessing dolomite formation temperatures using Mg isotopes, offering crucial insights into the resolution of the “dolomite problem.”

Source: Scientific Reports

DOI: 10.1038/s41598-025-95540-7