岩漆是干旱和半干旱地区常见的覆盖在裸露岩石表层的深褐色物质,200多年前就有学者开始关注这种地质体。经过国内外学者的长期研究,学术界对岩漆的物质来源和组成已无太多争议,岩漆的环境变化指示意义研究取得丰富成果,尤其是岩漆显微层理指示的环境变化成果颇丰。关于岩漆的形成原因,虽已形成物理化学成因和生物地球化学成因两大模型,但由于缺乏确切证据,岩漆的形成原因仍然存在争议。综合来看,目前人们对岩漆的研究均局限于现代地理环境中,对于地质历史时期形成的岩漆(即地层中的岩漆)从未有报道,而云南元谋干热河谷及土林地层中发现的“岩漆”或将成为国内岩漆研究的一个新方向,结合岩漆研究热点在全球的空间分布形式来看,岩漆可能指示了一种干旱的地理环境,而元谋干热河谷及土林地层中的岩漆,极有可能成为揭示金沙江干热河谷演化历史的重要证据,值得我们进一步研究。
Rock varnish is a common dark brown material covering bare rock surface in arid and semi-arid areas. More than 200 years ago, scholars began to pay attention to this geological body. After a long-term study by scholars at home and abroad, there is no much controversy about the material source and composition of rock varnish in academic circles. The significance of environmental change indicators of rock varnish has achieved rich results, especially the environmental change indicators of micro-stratification of rock varnish. Although physical-chemical and biogeochemical Genesis models have been established for the formation of rock varnish, there are still disputes about the formation of rock varnish due to lack of definite evidence. Generally speaking, the current research on rock varnish is limited to modern geographical environment. There has never been any report on rock varnish formed in geological history period (i.e. rock varnish in strata). The “rock varnish” found in Yuanmou dry-hot valley and soil forest strata in Yunnan may become a new direction of domestic research on rock varnish. In view of the global spatial distribution of hot spots in rock varnish research, it may indicate an arid geographical environment. Varnish in Yuanmou dry-hot valley and soil-forest strata is likely to be important evidence to reveal the evolution history of Jinsha River dry-hot valley, which deserves our further study.
岩漆,研究现状,金沙江干热河谷,演化历史, Rock Varnish Research Status Dry-Hot Valley of the Jinsha River Evolution History岩漆研究现状与展望
在国外,岩漆最早由被称为“岩漆之父”的亚历山大·冯·洪堡(Alexander von Humboldt)于1812年在奥里科诺河(发源于南美洲委内瑞拉与巴西交界的帕里马山脉)首先观察到并对其进行了描述 [4] ,此后,一场关于岩漆物质来源的争论一直从19世纪持续到了20世纪中后期。伴随电子显微镜技术的不断成熟与应用,人们对于岩漆的物质来源基本上达成了共识,与此同时,岩漆的物质组成也逐渐变得清晰起来。之后,岩漆的研究重点转移到了岩漆成因上。但到目前为止,由于缺乏确切证据,人们对于岩漆的成因仍然存在争议。伴随岩漆成因理论的研究,有关岩漆的环境变化指示意义研究亦取得了一系列重要成果:最早,Bauman A.J. (1976)和Dorn et al. (1981)发现碱性增加有碍微生物对锰的氧化 [5] [6] ;此后,Dorn R.I. (1984)的电子探针分析报告指出:岩漆中的显微层理的Mn/Fe比值可能反映过去风沙碱度水平值的波动及可能的气候变化,而这一陆地环境变化的新指标可能在研究地貌、考古学、古气候及第四纪干旱环境研究方面有着重要意义 [7] 。直到1990年,Dorn R. I.才最终证实:不论是物理化学成因模型还是生物地球化学模型,大气环境中的碱度(pH值)都会影响岩漆形成过程中锰的富集 [8] 。之后,岩漆的显微层理及其环境变化指示意义逐渐成为研究热点并取得重要成果:Broecker W. S. (1994)的研究指出:美国西南部岩漆中富含锰的黑色微层理的形成,在时间上与北大西洋地区末次冰期中出现的Heinrich气候事件具有良好的对应关系 [9] ;Lui T., Broecker W. S. , Bell J. B.等(1999)也指出:岩漆中黑色微层理形成于相对湿润的气候环境,而橙色微层理则形成于相对干旱的气候 [10] ,但到此时,有关岩漆的成因仍然没有定论。近些年,随着对岩漆成因理论的进一步深入研究,国外研究者开始认识到,要用单一的某一种假说试图解释岩漆的成因是行不通的,岩漆的成因研究应该通过辩证分类、系统分析的方法找出不同类型岩漆的成因才是可行的,为此,Macholdt D. S. et al. (2017)通过采集来自北美洲、亚洲和非洲等地的大量岩漆样品,并通过对比分析其形成环境、微观结构和化学成分等,最终建议将岩漆分为I-V型 [11] ,其典型特征见表1。研究发现,气候差异和生物活性的不同可能是导致不同类型岩漆形态和矿物多样性的重要原因 [12] 。近两年,对于岩漆的研究范围甚至已扩展至南极洲的麦克默多干燥谷 [13] ,而DNA元基因组测序方法也开始用于研究在岩漆的形成过程中是否有微生物的作用,研究表明:虽然没有发现酶直接参与岩漆形成的证据,但也不能排除检测到的微生物的间接影响 [14] 。时至今日,关于岩漆的成因仍然没有一个确切说法,而争论的焦点实则在于岩漆形成过程中是否有微生物的作用,对此,相关研究仍在继续。
Classification of rock lacquer types by structure and chemical composition [11
随着岩漆研究的不断深入,对岩漆的关注甚至到了南极洲和火星。但从未有学者关注过地层中的“岩漆”,也就是地质历史时期形成的岩漆被保留在了地层之中。笔者在野外考察时发现,在云南楚雄元谋干热河谷中分布有大量岩漆(图3),从海拔928米的元谋江边乡到海拔2114米的元谋东山顶皆有分布,同时,在元谋土林铁质胶结层表层还发现了正在形成的岩漆(图4)以及元谋土林地层中铁质胶结层表层的“岩漆” (图5)。无独有偶,国外学者在沙特阿拉伯西南部的瓦伊德砂岩(Wajid Sandstone)中也发现了类似于土林地层中的铁质胶结层(ferruginous cement) (图6),并且对该胶结层单体(lower red unit “LRU”)的研
李伟康,苏 怀,潘钰涵. 岩漆研究现状与展望Research Status and Prospect of Rock Varnish[J]. 地理科学研究, 2019, 08(03): 264-274. https://doi.org/10.12677/GSER.2019.83028
参考文献ReferencesEngel, C.G. and Sharp, R.P. (1958) Chemical Data on Desert Varnish. Geological Society of America Bulletin, 69, 487-518. <br>https://doi.org/10.1130/0016-7606(1958)69[487:CDODV]2.0.CO;2Hunt, C.B. (1954) Desert Var-nish. Science, 120, 183-184. <br>https://doi.org/10.1126/science.120.3109.183Lu, A., Li, Y., Ding, H., et al. (2019) Photoelectric Conversion on Earth’s Surface via Widespread Fe- and Mn-Mineral Coatings. Proceedings of the National Academy of Sciences of the United States of America, 116, 9741-9746.
<br>https://doi.org/10.1073/pnas.1902473116Alexander, V.H., Aime, B. and Ross, T. (1907) Personal Narrative of Travels to the Equinoctial Regions of America during the Years 1799-1804. George Bell & Sons, London. <br>https://doi.org/10.5962/bhl.title.23548Bauman, A.J. (1976) Desert Varnish and Marine Ferromanganese Oxide Nodules: Congeneric Phenomena. Nature, 259, 387-388. <br>https://doi.org/10.1038/259387a0Dorn, R.I. and Oberlander, T.M. (1981) Microbial Origin of Desert Varnish. Science, 213, 1245-1247.
<br>https://doi.org/10.1126/science.213.4513.1245Dorn, R.I. (1984) Cause and Implications of Rock Varnish Microchemical Laminations. Nature, 310, 767-770.
<br>https://doi.org/10.1038/310767a0Dorn, R.I. (1990) Quaternary Alkalinity Fluctuations Recorded in Rock Varnish Microlaminations on Western U.S.A. Volcanics. Palaeogeography, Palaeoclimatology, Palaeoecology, 76, 291-310.
<br>https://doi.org/10.1016/0031-0182(90)90117-PBroecker, W.S. (1994) Massive Iceberg Discharges as Trig-gers for Global Climate Change. Nature, 372, 421-424.
<br>https://doi.org/10.1038/372421a0Lui, T., Broecker, W.S., Bell, J.B. and Mandeville, C.W. (1999) Terminal Pleisrocene Wet Event Recorded in Rock Varnish from the Las Valley, Southern Nevada. Palaeogeography, Palaeo-climatology, Palaeoecology, 161,423-433.Macholdt, D.S., Jochum, K.P., Pöhlker, C., et al. (2017) Characteri-zation and Differentiation of Rock Varnish Types from Different Environments by Microanalytical Techniques. Chemical Geology, 459, 91-118.
<br>https://doi.org/10.1016/j.chemgeo.2017.04.009Xu, X.-M., Li, Y., Li, Y., et al. (2017) Spectral Characteristics of Rock Varnish from Arid and Humid Regions in China. Bulletin of Mineralogy Petrology & Geochemistry, 36, 299-307.Zerboni, A. and Guglielmin, M. (2017) Dust Input in the Formation of Rock Varnish from the Dry Val-leys (Antarctica). American Geophysical Union.Langyona, N., Maier, S., Macholdt, D.S., et al. (2018) Insights into Microbial Involvement in Desert Varnish Formation Retrieved from Metagenomic Analysis. Environmental Mi-crobiology Reports, 10, 264-271.
<br>https://doi.org/10.1111/1758-2229.12634朱显谟. 论原始土壤的成土过程[J]. 中国科学B辑, 1983, 3(10): 920-925.张裕明, 柳覃卓, 李树伟. 中国西部甘新边界地区岩漆阳离子比率测年曲线的建立及其应用[J]. 地震地质, 1990, 12(3): 251-261.尹玉军, 陈静生. 一种利用岩漆测定年龄和研究古气候的新方法[J]. 地球科学进展, 1991, 6(2): 75-78.周本刚, 柳覃卓, 张裕明. 新疆北天山地区岩漆显微层理及其古气候意义[J]. 科学通报, 1999, 44(13): 1445-1448.Xu, X., Ding, H., Li, Y., et al. (2018) Mineralogical Characteristics of Mn Coatings from Different Weathering Environments in China: Clues on Their Formation. Mineralogy and Petrology, 112, 671-683.
<br>https://doi.org/10.1007/s00710-018-0564-0Bard, J.C., Asaro, F. and Heizer, R.F. (2010) Perspectives on the Dating of Prehistoric Great Basin Petroglyphs by Neutron Activation Analysis. Archaeometry, 20, 85-88. <br>https://doi.org/10.1111/j.1475-4754.1978.tb00217.xBirot, P. (1969) The Cycle of Erosion in Different Cli-mates. University of California Press, Berkeley, CA.Holmes, A. (1965) Principles of Physical Geology. Ronald Press, New York.Hume, W.F. (1925) Geology of Egypt. The Surface Features of Egypt, Their Determining Causes and Relation to Geologic Structure, Vol. 1. Government Press, Cairo.Linck, G. (1901) ÜberdiedunkelenRinden der Gesteine der Wüste. Jenaische Zeitschrift für Naturwissenschaft, 35, 329-336.Linck, G. (1928) ÜberSchutzrinden. Chemie der Erde, 4, 67-79.Lucas, A. (1905) The Blackened Rocks of the Nile Cataracts and of the Egyptian Deserts. National Printing Department, Cairo.Marcus, M.G. and Brazel, A.J. (1992) Summer Dust Storms in the Arizona Desert. In: Janelle, D.G., Ed., Geographical Snapshots of North America, Guilford Press, New York, 411-415.Merrill, G.P. (1898) Desert Varnish. Bulletin of the United States Geological and Geographical Survey, 150, 389-391.Peel, R.F. (1960) Some Aspects of Desert Geomorphology. Geography, 45, 241-262.Walther, J. (1891) Die Denudation in der Wüste. Akademi der Wissenschaften: Mathematischk-Physicalische Klasse. Abhandlungen, 16, 435-461.Wilhelmy, H. (1964) Cavernous Rock Surfaces in Semi-Arid and Arid Climates. Pakistan Geographical Review, 19, 8-13.Woolnough, W.G. (1930) The Influence of Climate and Topography in the Formation and Distribution of Products of Weathering. Geological Magazine, 67, 123-132. <br>https://doi.org/10.1017/S0016756800099015Dorn, R.I., Krinsley, D.H. and Ditto, J. (2012) Alexander von Humbodlt’s Initiation of Rock Coating Research. Geology, 12, 1-12.Langworthy, K.A., Krinsley, D.H. and Dorn, R.I. (2010) High Resolution Transmission Electron Microscopy Evaluation of Silica Glaze Reveals New Textures. Earth Surface Processes & Landforms, 35, 1615-1620.
<br>https://doi.org/10.1002/esp.2061Liu, T. and Broecker, W.S. (2000) How Fast Does Rock Varnish Grow? Geology, 28, 183-186.
<br>https://doi.org/10.1130/0091-7613(2000)28<183:HFDRVG>2.0.CO;2Liu, T. and Broecker, W.S. (2008) Rock Varnish Evidence for Latest Pleistocene Millennial-Scale Wet Events in the Drylands of Western United States. Geology, 36, 403-406. <br>https://doi.org/10.1130/G24573A.1Perry, R.S. and Adams, J.B. (1978) Desert Varnish: Evidence for Cyclic Deposition of Manganese. Nature, 276, 489-491. <br>https://doi.org/10.1038/276489a0Dorn, R.I. (2009) Desert Rock Coatings. In: Parsons, A.J. and Abrahams, A.D., Eds., Geomorphology of Desert Environments, Springer, Dordrecht, 153-186. <br>https://doi.org/10.1007/978-1-4020-5719-9_7Krinsley, D., Dorn, R. and Anderson, S. (1990) Factors that May Interfere with the Dating of Rock Varnish. Physical Geography, 11, 97-119. <br>https://doi.org/10.1080/02723646.1990.10642396Krinsley, D. (1998) Models of Rock Varnish Formation Constrained by High Resolution Transmission Electron Microscopy. Sedimentology, 45, 711-725. <br>https://doi.org/10.1046/j.1365-3091.1998.00172.xKrinsley, D., Dorn, R. and Tovey, N.K. (1995) Nanometer-Scale Layering in Rock Varnish: Implications for Genesis and Paleoenvironmental Interpretation. The Journal of Geology, 103, 106-113. <br>https://doi.org/10.1086/629726Krinsley, D. and Rusk, B.G. (2000) Bacterial Presence in Layered Rock Varnish-Possible Mars Analog? International Conference on Mars Polar Science & Exploration, Reykjavik, Iceland, 21-25 August 2000, 98.Potter, R.M. and Rossman, G.R. (1979) The Manganese- and Iron-Oxide Mineralogy of Desert Varnish. Chemical Geology, 25, 79-94. <br>https://doi.org/10.1016/0009-2541(79)90085-8Thiagarajan, N. and Lee, C.T.A. (2004) Trace-Element Evidence for the Origin of Desert Varnish by Direct Aqueous Atmospheric Deposition. Earth and Planetary Science Letters, 224, 131-141.
<br>https://doi.org/10.1016/j.epsl.2004.04.038Sarmast, M., Farpoor, M.H. and Esfandiarpour Boroujeni, I. (2017) Soil and Desert Varnish Development as Indicators of Landform Evolution in Central Iranian Deserts. Catena, 149, 98-109. <br>https://doi.org/10.1016/j.catena.2016.09.003Hooke, R.L., Yang, H. and Weiblen, P.W. (1969) Desert Varnish: An Electron Probe Study. The Journal of Geology, 77, 275-288. <br>https://doi.org/10.1086/627435Smith, B.J. and Whalley, W.B. (1988) A Note on the Characteristics and Possible Origins of Desert Varnishes from Southeast Morocco. Earth Surface Processes and Landforms, 13, 251-258. <br>https://doi.org/10.1002/esp.3290130306Allen, C.C., Probst, L.W., Flood, B.E., et al. (2004) Meridiani Planum Hematite Deposit and the Search for Evidence of Life on Mars—Iron Mineralization of Microorganisms in Rock Varnish. Icarus, 171, 20-30.
<br>https://doi.org/10.1016/j.icarus.2004.04.015Gorbushina, A.A. (2003) Microcolonial Fungi: Survival Potential of Terrestrial Vegetative Structures. Astrobiology, 3, 543-554. <br>https://doi.org/10.1089/153110703322610636Krumbein, W.E. (1968) Über den Einfluß der Mikroflora auf die exogene Dynamik (Verwitterung und Krustenbildung). Geologische Rundschau, 58, 333-363. <br>https://doi.org/10.1007/BF01820710Kuhlman, K.R., Fusco, W.G., La Duc, M.T., et al. (2006) Diversity of Microorganisms within Rock Varnish in the Whipple Mountains, California. Applied and Environmental Microbiology, 72, 1708-1715.
<br>https://doi.org/10.1128/AEM.72.2.1708-1715.2006Parchert, K.J., Spilde, M.N., Porras-Alfaro, A., et al. (2012) Fungal Communities Associated with Rock Varnish in Black Canyon, New Mexico: Casual Inhabitants or Essential Partners? Geomicrobiology Journal, 29, 752-766.
<br>https://doi.org/10.1080/01490451.2011.619636Perry, R.S. and Kolb, V.M. (2004) Biological and Organic Constituent of Desert Varnish: Review and New Hypotheses. Proceedings of Instruments, Methods, and Missions for Astrobiology, 5163, 202-217.
<br>https://doi.org/10.1117/12.509695Staley, J.T., Jackson, M.J., Palmer, F.E., et al. (1983) Desert Varnish Coatings and Microcolonial Fungi on Rocks of the Gibson and Great Victoria Desert, Australia. AGSO Journal of Australian Geology & Geophysics, 8, 83-87.White, C.H. (1924) Desert Varnish. American Journal of Science, 7, 413-420. <br>https://doi.org/10.2475/ajs.s5-7.41.413Perry, R.S., Lynne, B.Y., Sephton, M.A., et al. (2006) Baking Black Opal in the Desert Sun: The Importance of Silica in Desert Varnish. Geology, 34, e122-e123.Perry, R.S., Lynne, B.Y., Sephton, M.A., et al. (2006) Baking Black Opal in the Desert Sun: The Importance of Silica in Desert Varnish. Geology, 34, 537-540.Dorn, R.I. (1998) Rock Coatings. Elsevier, Amsterdam.Dorn, R.I. and Krinsley, D. (2011) Spatial, Temporal and Geographic Considerations of the Problem of Rock Varnish Diagenesis. Geomorphology, 130, 91-99. <br>https://doi.org/10.1016/j.geomorph.2011.02.002Dorn, R.I., Krinsley, D.H., Liu, T., et al. (1992) Manganese-Rich Rock Varnish Does Occur in Antarctica. Chemical Geology, 99, 289-298. <br>https://doi.org/10.1016/0009-2541(92)90182-5Potter, R.M. and Rossman, G.R. (1977) Desert Varnish: The Importance of Clay Minerals. Science, 196, 1446-1448.
<br>https://doi.org/10.1126/science.196.4297.1446Elvidge, C.D. and Moore, C.B. (1980) Restoration of Petroglyphs with Artificial Desert Varnish. Studies in Conservation, 25, 108-117. <br>https://doi.org/10.1179/sic.1980.25.3.108Dorn, R.I. and Oberlander, T.M. (1982) Rock Varnish. Progress in Physical Geography: Earth and Environment, 6, 317-367. <br>https://doi.org/10.1177/030913338200600301Liu, T. and Broecker, W.S. (2013) Millennial-Scale Varnish Microlamination Dating of late Pleistocene Geomorphic Features in the Drylands of Western USA. Geomorphology, 187, 38-60.
<br>https://doi.org/10.1016/j.geomorph.2012.12.034Goldsmith, Y., Stein, M. and Enzel, Y. (2014) From Dust to Varnish: Geochemical Constraints on Rock Varnish Formation in the Negev Desert, Israel. Geochimica et Cosmochimica Acta, 126, 97-111.
<br>https://doi.org/10.1016/j.gca.2013.10.040Macholdt, D.S., Jochum, K.P., Pöhlker, C., et al. (2015) Microanalytical Methods for in Situ High-Resolution Analysis of Rock Varnish at the Micrometer to Nanometer Scale. Chemical Geology, 411, 57-68.
<br>https://doi.org/10.1016/j.chemgeo.2015.06.023Mancinelli, R.L., Bishop, J.L. and De, S. (2002) Magnetite in Desert Varnish and Applications to Rock Varnish on Mars. 2002 Lunar & Planetary Science Conference, League City, TX, 11-15 March 2002.Ward, J.G., Kirkland, L.E., Keller, D., et al. (2001) Terrestrial Rock Varnish: A Key to Understanding the Surface Composition of Mars. 2001 Lunar & Planetary Science Conference, Houston, TX, 12-16 March 2001.El Aal, A.A. and Nabawy, B.S. (2017) Implications of Increasing the Ferruginous Cement on the Physical and Mechanical Properties of the Cambro-Ordovician Wajid Sandstone in Southwest Saudi Arabia: Applications for Construction Purposes. Bulletin of Engineering Geology and the Environment, 78, 817-836.
<br>https://doi.org/10.1007/s10064-017-1115-3