Field observation shows that multiple phases of calcite veins occur along fractures in the Ordovician

Permian and Triassic of overthrust belts and fold-thrust belts in Jingshan region

Mid-Yangtze.Using rare earth elements(REE)

electron microprobe

oxygen isotope

fluid inclusions and basin modeling

this paper analyzed the genesis of these calcite veins.The REE of calcite veins in the Ordovician and Triassic are characterized by enrichment of LREE

loss of HREE and obvious positive Eu anomaly

indicating that their vein-froming fluids were affected by hydrothermal fluids.Calcite veins in the Permian feature in low REE

only slight enrichment of LREE

flat HREE patterns

and the presence of a moderate negative Ce anomaly

implying that their vein-froming fluids originated from meteoric water infiltration.Analysis of Fe and Mn through electron microprobe indicates that some calcite veins in the Ordovician were derived from the dissolution of surrounding carbonate rocks

the calcite veins in the Permian were derived from leaching and dissolution of carbonates by meteoric water

and those in the Triassic were related to the dissolution of carbonate derived from other horizons.Combined with burial and thermal history modeling of pseudo-wells

analysis of oxygen isotope temperatures and homogenized temperature of fluid inclusions show that the calcite vines filling fractures in these 3 sequences were formed at 150~60 Ma ago at burial depth in the range from 2 000 m to 2 500 m.Based on a comprehensive analysis of geochemical behaviors of the calcite veins

it is believed that hydrothermal fluids

vein-froming fluids and meteoric water infiltration associated with tectonic compression and uplifting during Yanshan Orogeny may have damaged petroleum preservation conditions in Jingshan region to some extent.