The south basin of the South Yellow Sea basin is an extension of lower Yangtze platform to the northeast.The south basin is very similar to the Subei basin in regional structure and geological characteristics of oil and gas.Successful exploitation of Zhujiadun gas field in Subei basin provides experience for explorations in the south basin.The authors compared reservoir conditions of south basin with the Zhujiadun gas field based on analysis of reservoir characteristics in Zhujiadun gas field and found they were very alike.The authors concluded that south basin of the South Yellow Sea basin possesses good exploration prospect,the gas fields have ancient generation and young accumulation,and the target is the belt of deep depression on the side of large fault.
The Coleman Member of the ea. 2.3 Ga Gowganda Formation is beautifully exposed in a glacially polished outcrop near Cobalt, Ontario. This lithologic unit is a glacial diamictite, or tillite, consisting of clasts up to 1.5 m in diameter embedded in a silty to sandy matrix. More than half of the clasts display alteration rinds. On granite clasts these consist of a pale pink outer rim and a dark inner rim, in which orthoclase has been replaced by what is now chlorite. The rinds are inferred to have initially developed as a result of chemical weathering before the clasts were deposited as part of the tillite, and to have been modified by post-depositional metamorphism. The chlorite in the rinds contains Mg and Fe in approximately the same proportion as in the unweathered clasts. The chlorite was probably generated by the low-grade metamorphism of smectites produced by the reaction of feldspars with O2-free groundwater carrying Fe+2 and Mg+2. The absence of O2 in these ground waters is consistent with the deposition of the Gowganda Formation before the rise of O2 in the atmosphere ca. 2.25 Ga.
According to the analysis of conventional thin sections,columnar thin sections, mercury curve and data of porosity permeability,lithologic characteristics,pore texture,reservoir space,petrophysical property,diagenetic type of T_(3)x~(4)have been discussed.Pore development is considered that is controlled by both of sedimentary conditions and burial diagenesis.Mechanical compaction is the main factor to result in worsening of sand pore texture; Authigenetic cements in reservoirs is developed,which is the main reason to result in reservoir worsening;Secondary pore produced by dissolution is favorable to gas accumulation in reservoirs,thus forming good reservoirs.
This paper presents the position, distribution, stratigraphy and geotechology of Chenkou Mn Deposit. Its geologic features are described in detail; its origin of ore deposit is analysed and the conclusion is drawn that this deposit is a precipitated Mn carbonate ore deposit formed in stagnant bay environment. Based on the information available, this paper expects several ore-striking areas.
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