SWIR Spectral Characteristics and Mineral Phase Transformations: Multi-Indicator Synergistic Response for Granite Weathering Classification
ZHANG Shuo1, 2, 3, LI Yu1, JIANG Tong1*, HUANG Jian-han1, HUANG Yin-wei1, 4, TIAN Jing-chun3, SHAN Mao-yu1, LI Pei-yao1
1. North China University of Water Resources and Electric Power, Zhengzhou 450046，China
2. State Key Loboratory of Geohazard Prevention and Geoenvironment Protection，Chengdu University of Technology，Chengdu 610059，China
3. Institute of Sedimentary Geology，Chengdu University of Technology，Chengdu 610059，China
4. Zhejiang Huadong Geotechnical Investigation & Design Institite Co., Ltd.，Hangzhou 310030，China
Abstract：The weathering degree of granite is a critical factor governing the engineering geological characteristics and disaster risks of rock masses. However, traditional assessment methods suffer from limitations in single-dimensional parameter characterization and invasive sampling that compromises rock integrity. This study integrates chemical weathering indices and mineralogical features derived from short-wave infrared (SWIR) spectroscopy to establish a multi-dimensional, non-destructive evaluation framework for granite weathering. Taking the typical granite weathering profile in Guangde City as the research object, combined with physical and mechanical tests, X-ray fluorescence spectroscopy(XRF),and SWIR spectroscopy analysis, the co-evolution mechanism of element migration, mineral phase transition, and mechanical degradation during weathering was systematically revealed. The study reveals significant correlations between the physical-mechanical properties and chemical weathering indices of granite with varying weathering degrees. The STI index exhibits a distinct relationship with porosity. At the same time, CIA, CIX, WIC, WIG, and Rb/Sr ratios demonstrate significant linear relationships with dry density, water absorption, compressive strength, and ultrasonic wave velocity. SWIR spectral characteristics can dynamically characterize the mineral transformation sequence. The completely weathered layer exhibits absorption features dominated by montmorillonite and kaolinite,while the highly weathered layer demonstrates absorption characteristics primarily composed of montmorillonite and illite. Moderately/slightly weathered layers display similar absorption features of montmorillonite and prehnite. However, the significantly reduced absorption peak depth in slightly weathered layers, resulting from lower contents of montmorillonite and prehnite, serves as a diagnostic characteristic for identifying moderately/slightly weathered layers.The spectral absorption characteristics of minerals, including peak morphology, depth, and ratio parameters, exhibit quantitative correlations with established chemical weathering indices. Spectral analysis of mineral phase transformation processes reveals that the absorption feature depths at 1 400 nm (d1 400) and 2 200 nm (d2 200) demonstrate positive correlations with clay mineral content. Furthermore, the characteristic ratios of d1 400/d1 900 and d2 200/d1 900 serve as effective indicators of clay mineral weathering intensity, with higher values corresponding to more advanced weathering stages. Compared to the Si-Ti and Rb/Sr ratios, the chemical weathering indices defined based on mobile oxides, along with absorption peak depths and their ratios, demonstrate superior performance in evaluating granite weathering intensity. The proposed quantitative classification framework, built on the synergistic response of mineral transformations and spectral signatures, provides theoretical and methodological support for rapid identification of granite weathering grades and disaster risk mitigation.
[1] GU Qi-xiong, HUANG Zhen, ZHONG Wen, et al(古启雄, 黄 震, 钟 文, 等). Chinese Journal of Rock Mechanics and Engineering(岩石力学与工程学报), 2023, 42(6): 1450.
[2] XU Xiao-Chun, AN Yu-hua, XU Xin-yue, et al(徐晓春, 安昱华, 许心悦, 等). Journal of Earch Sciences and Environment(地球科学与环境学报), 2020, 42(1): 15.
[3] MA Hai-yi, LU Zu-de(马海毅, 鲁祖德). Rock and Soil Mechanics(岩土力学), 2012, 33(2): 361.
[4] Liu X, Zhang X, Kong L, et al. Engineering Geology, 2022, 305: 106723.
[5] YAO Yu-peng, LIU Xin, LIU Zhi-qing(么玉鹏, 刘 鑫, 刘志清). Journal of Liaoning Technical University(Natural Science)[辽宁工程技术大学学报(自然科学版)], 2019, 38(2): 118.
[6] LU Zhao-zhen(陆兆溱). Engineering Geology (2nd Edition)[工程地质学(第2版)]. Beijing: China Water & Power Press(北京：中国水利水电出版社), 2001.
[7] LI Ye-xue, XIE Xiang-dong, QIN Li(李业学, 谢向东, 秦 丽). Journal of Vibration and Shock(振动与冲击), 2012, 31(2): 169.
[8] YE Fei, CHEN Wen-wu, LIANG Xing-zhou, et al(叶 飞, 谌文武, 梁行洲, 等). Jouranl of Engineering Geology(工程地质学报), 2016, 24(6): 1286.
[9] Yang H, Huang G, Chen C, et al. Bulletin of Engineering Geology and the Environment, 2024, 83(5): 193.
[10] CHEN Bo, YANG Jiang-hai, REN Jun-tong, et al(陈 波, 杨江海, 任俊童, 等). Journal of Earth Science(地球科学), 2025, 50(7): 2720.
[11] Nesbitt H W, Young G M. Nature, 1982, 299(5885): 715.
[12] Garzanti E, Padoan M, Setti M, et al. Chemical Geology, 2014, 366: 61.
[13] Colman S M. Chemical Weathering of Basalts and Andesites: Evidence from Weathering Rinds. U.S. Geological Survey, 1982.
[14] Gong Q, Deng J, Wang C, et al. Journal of Geochemical Exploration, 2013, 128: 14.
[15] Jayawardena U de S, Izawa E. Engineering Geology, 1994, 36(3-4): 303.
[16] Dasch E J. Geochimica et Cosmochimica Acta，1969, 33(12): 1521.
[17] Loubser M, Verryn S. South African Journal of Geology, 2008, 111(2-3): 229.
[18] WU Bei-juan, PENG Bo, ZHANG Kun, et al(吴培娟，彭 渤，张 坤，等). Acta Geological Sinica(地质学报), 2016, 90(4): 818.
[19] Huang X, Guo F, Ding X, et al. Solid Earth Sciences, 2025, 10(1): 100201.
[20] Clark R N, King T V V, Klejwa M, et al. Journal of Geophysical Research: Solid Earth, 1990, 95(B8): 12653.
[21] Zhao L, Hong H, Liu J, et al. Palaeogeography, Palaeoclimatology, Palaeoecology, 2018, 512: 80.
[22] JIANG Hong-jun, CHEN Hua-yong, WANG Peng, et al(江宏君, 陈华勇, 王 朋, 等). Geotectonica et Metallogenia(大地构造与成矿学), 2023, 47(6): 1291.
[23] Dufrechou G, Grandjean G, Bourguignon A. Geoderma, 2015, (243-244): 92.
[24] GUO Na, WANG Xin-chen(郭 娜, 王馨晨). Spectroscopy and Spectral Analysis(光谱学与光谱分析), 2023, 43(11): 3492.
[25] Heidari M, Momeni A A, Naseri F. Engineering Geology, 2013, 166: 65.
[26] WEI Qing, FAN Hong-rui, LAN Ting-guang, et al(卫 清, 范宏瑞, 蓝廷广, 等). Acta Petrologica Sinica(岩石学报), 2015, 31(4): 1049.
[27] WEI Shou-shu, MA Ling-ya, LIANG Xiao-liang, et al(韦寿淑, 马灵涯, 梁晓亮, 等). Acta Mineralogica Sinica(矿物学报), 2021, 41(1): 85.
[28] SUN Hou-yun, SUN Xiao-ming, WEI Xiao-feng, et al(孙厚云, 孙晓明, 卫晓锋, 等). Geology in China(中国地质), 2022, 49(4): 1088.
[29] SHANG Yan-jun, WU Hong-wei, QU Yong-xin(尚彦军, 吴宏伟, 曲永新). Chinese Journal of Geology(地质科学), 2001, 36(3): 279.
[30] ZHANG Long, LIU Chi-yang, LEI Kai-yu, et al(张 龙, 刘池洋, 雷开宇, 等). Acta Geologica Sinica(地质学报), 2017, 91(6): 1345.
[31] YU Li-dong, SUN Hai-wei, ZHANG Jing, et al(于立栋, 孙海微, 张 静, 等). Acta Petrologica Sinica(岩石学报), 2020, 36(5): 1597.
[32] WANG Yong-jian, NIE Jiang-tao, LIN Jin-rong, et al(王勇剑, 聂江涛, 林锦荣, 等). Acta Petrologica Sinica(岩石学报), 2022, 38(9): 2865.
[33] Ma R, Liu C, Greskowiak J, et al. Journal of Contaminant Hydrology，2014, 156: 27.
[34] FAN Hong-rui，XIE Yi-han，WANG Kai-yi, et al(范宏瑞, 谢奕汉, 王凯怡, 等). Earth Science Frontiers(地学前缘), 2001, 8(4): 289.
[35] Hossain H Z, Kawahata H, Roser B P, et al. Geochemistry, 2017, 77(3): 443.
[36] McLennan S M. The Journal of Geology, 1993, 101(2): 295.
[37] YANG Zhi-quan, LI Fei-yang, GAN Jing, et al(杨志全, 李飞洋, 甘 进, 等). Journal of Mining and Strata Control Engineering(采矿与岩层控制工程学报), 2024, 6(1): 013036.
[38] XIE Xin-hui, DENG Hu-cheng, HU Lan-xiao, et al(解馨慧, 邓虎成, 胡蓝霄, 等). Oil & Gas Geology(石油与天然气地质), 2024, 45(4): 1079.
[39] ZHANG Gong-ji, LI Chang-dong, MENG Jie, et al(张功基, 李长冬, 孟 杰, 等). The Chinese Journal of Geological Hazard and Control(中国地质灾害与防治学报), 2025，36(4): 15.
[40] HUANG Man, LU Meng-yi, WU Yue-wei, et al(黄 曼, 逯梦怡, 吴月伟, 等). Chinese Journal of Rock Mechanics and Engineering(岩石力学与工程学报), 2025, 44(4): 827.
