Hydrated sulfate minerals (bloedite and polyhalite): formation and paleoenvironmental implications
- PDF / 3,120,900 Bytes
- 12 Pages / 595.276 x 790.866 pts Page_size
- 26 Downloads / 260 Views
ORIGINAL ARTICLE
Hydrated sulfate minerals (bloedite and polyhalite): formation and paleoenvironmental implications Minghui Li1,2 · Xiaomin Fang2,3,4 · Albert Galy5 · Huiling Wang1 · Xiangsuo Song6 · Xiaoxiao Wang1,3 Accepted: 12 October 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Salt minerals that are used to reconstruct paleoenvironments should be either primary or samples that provide primarylevel information. Using hydrated sulfate minerals that are commonly found in saline lacustrine sediments (i.e., bloedite and polyhalite), the paleoenvironment of the Qaidam Basin, in the northeastern Tibetan Plateau was reconstructed. In this study, we determined the primary and secondary mineral formations based on their S, Mg, H, and O isotopic compositions. While polyhalite is a secondary mineral, bloedite precipitated out from the brine at 0.39 Ma, and ultimately became a secondary mineral at 0.36 Ma. The bloedite and polyhalite Mg isotopes did not record primary signals, but they still provide valuable insights into the paleoenvironments in which they formed. The climate in our study area is very dry; based on the temperature of the brine, this region experienced high temperatures at 0.39 Ma, 0.36 Ma, and 0.12 Ma. We identified one major chemical inconsistency: the bloedite 18O-hydrated water and 18O-SO4 values had basically achieved equilibrium, while the polyhalite and gypsum exhibited no oxygen exchange between their SO4 and hydrated water components. The possible reason for the inconsistency was the differences in mineral crystal structures. We hope that future studies will reconcile this conflicting information. Keywords Magnesium isotopes · Sulfur isotopes · Oxygen and hydrogen isotopes · Salt minerals
Introduction
* Minghui Li [email protected] 1
Key Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences (ITP, CAS), Beijing 100101, China
2
CAS Center for Excellence in Tibetan Plateau Earth Sciences, Beijing 100101, China
3
University of Chinese Academy of Sciences, Beijing 100049, China
4
Key Laboratory of Continental Collision and Plateau Uplift, ITP, CAS, Beijing 100101, China
5
Centre de Recherches Pétrographiques et Géochimiques (CRPG), UMR7358, CNRS-Université de Lorraine, 15 rue Notre Dame des Pauvres, 54501 Vandoeuvre les Nancy Cedex, France
6
Shandong Academy of Geosciences, Jinan 250013, China
Because most salt minerals are highly soluble in water, the reworking of salt crystals is very common. Therefore, to maintain the accuracy of a paleoenvironment reconstruction, it is best to study primary salt minerals or minerals that contain primary-level information. However, it is difficult to confirm that a given salt mineral sample is a primary mineral. Primary minerals are typically defined as minerals that directly precipitate from a solution, while those that form after the initial precipitation event are defined as secondary minerals (Ingerson 1968). Double salt
Data Loading...
