Scent of a myth: tectonics, geochemistry and geomythology at Delphi (Greece)

Extensive geochemical investigation (of water, travertine, soil and diffuse gas), coupled with geo-structural analysis, provides new insights into local fault–fluid interaction and allows us to pinpoint basic elements in the geological origin (or geomythology) of the Delphic Oracle, still debated by geologists. Delphi hosted the most famous oracle of antiquity, supposed to prophesy under the effects of intoxicating gas exhaling from a chasm in the ground. CO₂–H₂S-rich, ethylene-rich or CH₄-rich gases have been invoked to explain the mantic vapours. Although previous interpretations dismissed the results achieved by classical scholars, this study fits together history, archaeology, mythology and geology in a single coherent frame. We highlight that no hydrocarbon gas discharges are released at present to the surface in the area. The lack of any geochemical ‘anomaly’ indicates that the Delphi active fault does not at present constitute a preferential route for the circulation of thermogenic deep fluids. The mythological gas-exhaling chasm can plausibly be related to episodic seismic ruptures in the ancient past, which affected for a limited time gas pockets fed by a relatively deep confined hydrothermal system. The Delphi fault has produced shocks up to Ms=6.7 (1 August 1870), and similar seismic faulting events in the past could have episodically triggered CO₂–H₂S-rich emissions.

本研究通过对水体、钙华（travertine）、土壤及弥散性气体开展大规模系统性地球化学调查，辅以构造地质分析，为区域断层-流体相互作用机制提供了全新见解，同时精准厘定了德尔斐神谕（Delphic Oracle）地质起源（或地质神话学，geomythology）的核心要素，该议题至今仍在地质学界引发广泛争议。德尔斐是古希腊最负盛名的神谕圣地，相传其神谕的预言能力源于地下裂隙释放的致醉气体。此前学界曾援引富含CO₂-H₂S、乙烯或甲烷的气体，用以解释这类神谕致幻蒸汽。尽管过往研究曾驳斥古典学者的相关研究结论，但本研究将历史学、考古学、神话学与地质学有机整合，构建了统一自洽的分析框架。本研究指出，该区域目前并无烃类气体向地表释放。未检测到任何地球化学异常，这表明德尔斐活动断层目前并非热成因深部流体循环的优势通道。传说中释放气体的裂隙，可合理归因于古代的间歇性地震破裂事件——这类事件曾在有限时段内激活由深部封闭热液系统补给的气藏。德尔斐断层曾发生过震级达Ms6.7的地震（1870年8月1日），过往类似的断层错动事件可能曾间歇性引发富含CO₂-H₂S的气体释放。