Based on drilling

logging and various test data

this paper studied the origin of deep-semi deep lacustrine dolostones of the Lower Cretaceous Tenggeer Formation in Baiyinchagan sag of Erlian Basin

Inner Mongolia.Core observation and thin section analysis data in combination with electron probe

energy spectrum

trace element and X-ray diffraction were used to analyze mineral composition and texture

structure of the rock.On this basis

we identified the origin of the dolostones.The results show that the dolostones(zeolitic dolostones and zeolite with single layer thickness of 0.2-1.5 m)in the study area are composed of ankerite(proportion of Fe is 0.5%-5%)

natrolite

analcite

sjogrenite

barite and pyrite.The dolomite crystals feature in size of 10-200 μm

wavy extinction

saddle morphology and development of fissures.These dolostones have muddy-micritic or intraclast(mainly from dolomites and zeolites)structures.Laminated

contemporaneous deformation

net-veined

and brecciated structures are common.GR is 700-1 100 API

which is 2-4 times as large as that of normal mudstones.U and Th content is up to 40-60 ppm and 60-100 ppm respectively.Trace elements

including Cu

Ni

Co

Fe and Mn

have a similar composition and distribution with the modern hydrothermal sediments on the Red Sea floor.The dolostones are distributed along the basement faults laterally.It is concluded that this is a set of 'white smoke chimney' hydrothermal dolostones.However

these sediments are rarely reported.The study of the chemical and thermodynamics process is deficient

and the deposition mechanism is not very clear.This research will be helpful for enriching the theory of sedimentology and discovering more mineral resources associated with hydrothermal sediments.