The geochemical indicators of the Middle Devonian Laohutou Formation in northern Guangdong reflect the geochemical characteristics of both terrestrial and marine facies,with an increasein Sr and La contents from continental to marine facies.The geochemical index of pH value of the sedimentary environment reflects the sudden changes in pH of sedimentary water and diagenetic water,which is an important controlling factor of Au precipitation.Cerium anomaly is an important indicator of oxidation-reduction sedimentary environment.The lower layer of geophysical barrier mudstone is the enrichment site of Au and other elements.The Early-Middle Devonian Yangxi Formation was a continental alluvial and fluvial layer.The first section of theMiddle DevonianLaohutou Formation was acontinentalalluvial layer,whilethe second section of which was the initial stage of large-scale marine transgression in the Middle Devonian.The Middle Devonian Qiziqiao Formation(D)2q was marine strata.
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