Geochemical characteristics of natural springs within the Lenglongling fault zone related to the Menyuan Ms 6.9 earthquake on January 8, 2022, NW China

IF 3.1 3区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Applied Geochemistry Pub Date : 2023-08-25 DOI:10.1016/j.apgeochem.2023.105767

Xiangxian Ma , Li Zhang , Zhi Chen , Yuanyuan Shao , Jianzhen Chen , Ruishou Ba , Maoliang Zhang , Giovanni Martinelli , Daniele L. Pinti , Xiaocheng Zhou , Guodong Zheng

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引用次数: 0

Abstract

Geofluids from natural springs connect with the crust and/or mantle in many cases, and their geochemical anomalies could be significant for the study on faults activity and even earthquakes. Several natural springs are distributed along the Lenglongling fault zone (LLLFZ) in the northeastern margin of the Tibetan Plateau, where the Ms 6.9 Menyuan earthquake occurred on January 8th, 2022. Based on chemical and isotopic compositions (δD, δ¹⁸O, δ¹³C, and ³He/⁴He) of water and gas samples, the origin of geofluids and their potential correlation with fault activity even including earthquakes are preliminarily assessed in this paper. The δ¹³C_CO2 values and ³He/⁴He ratios showed that the gas originating from the crust was associated with the metamorphism of carbonate rocks, whereas the δ¹⁸O and δD values of water samples indicated that the natural springs were predominantly infiltrated with precipitations from local mountains ranging 3.7 - 5.5 km in height. Obvious changes of Ca²⁺ and HCO₃⁻ concentrations in SZK spring waters in the surface rupture zones were observed in a short period (about three months) after the main shock, in contrast to those of the GSK springs far from the surface rupture zones. Such variations might be correlated with the stress increase prior to the 2022 Menyuan Ms 6.9 earthquake. The mechanical fracturing of surrounding limestone rocks during the slipping movement of LLLF could facilitate the water-rock interactions. Compared to three-month observations after the main shock, relatively higher concentrations of HCO₃⁻ and heavier δ¹⁸O_H₂_O values of the LHG springs were also observed in the short-term period. The shallow stored formation water might be squeezed along the cracks and rose to the surface during earthquake tremors, causing a sandblasting water phenomenon.

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与2022年1月8日门源6.9级地震有关的冷龙岭断裂带天然泉水地球化学特征

在许多情况下，来自天然泉水的地流体与地壳和/或地幔相连，它们的地球化学异常对断层活动甚至地震的研究可能具有重要意义。青藏高原东北缘冷龙岭断裂带(LLLFZ)沿线分布着几处天然泉水，该断裂带于2022年1月8日发生了门源6.9级地震。根据水、气样品的化学和同位素组成(δD、δ18O、δ13C和3He/4He)，初步评价了地流体的成因及其与断裂活动甚至地震的潜在相关性。δ13CCO2值和3He/4He比值表明，天然气来源于地壳，与碳酸盐岩的变质作用有关，而水样的δ18O和δD值表明，天然泉水主要被当地海拔3.7 ~ 5.5 km的山地降水渗透。在主震后较短时间内(约3个月)，SZK泉水中Ca2+和HCO3−浓度发生了明显变化，而远离表面破裂区的GSK泉水中Ca2+和HCO3−浓度变化明显。这种变化可能与2022年门源6.9级地震前的应力增加有关。在LLLF滑动运动过程中，周围灰岩的力学破裂有利于水岩相互作用。与主震后3个月的观测值相比，短时间内LHG泉的HCO3−浓度较高，δ18OH2O值较重。地震时，浅层储层水可能被挤压，沿裂缝上升至地表，形成喷砂水现象。

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来源期刊

Applied Geochemistry 地学-地球化学与地球物理

CiteScore

6.10

自引率

8.80%

发文量

272

审稿时长

65 days

期刊介绍： Applied Geochemistry is an international journal devoted to publication of original research papers, rapid research communications and selected review papers in geochemistry and urban geochemistry which have some practical application to an aspect of human endeavour, such as the preservation of the environment, health, waste disposal and the search for resources. Papers on applications of inorganic, organic and isotope geochemistry and geochemical processes are therefore welcome provided they meet the main criterion. Spatial and temporal monitoring case studies are only of interest to our international readership if they present new ideas of broad application. Topics covered include: (1) Environmental geochemistry (including natural and anthropogenic aspects, and protection and remediation strategies); (2) Hydrogeochemistry (surface and groundwater); (3) Medical (urban) geochemistry; (4) The search for energy resources (in particular unconventional oil and gas or emerging metal resources); (5) Energy exploitation (in particular geothermal energy and CCS); (6) Upgrading of energy and mineral resources where there is a direct geochemical application; and (7) Waste disposal, including nuclear waste disposal.