Magmatic hydrothermal fluid genesis of zeolite in the Paleogene Kongdian Formation of Zaoyuan oilfield,Bohai Bay Basin,China

Electronic probe,fluid inclusion homogenization temperature,Raman spectroscopy and laser ablation inductively coupled plasma mass spectrometry were utilized to identify the hydrothermal fluid-rock interactions in the second member of the Paleogene Kongdian Formation of Zaoyuan oilfield in Bohai Bay Basin(Kong 2 Member for short)of Well Z56 to find out the relationship between zeolite and hydrothermal fluid.The experimental results show that:(1)Pyrobitumen coexists with hydrothermal fluid characteristic minerals such as chlorite,barite,chalcopyrite,pyrite,natrolite and analcime in mudstone fractures.(2)The temperatures calculated from laser Raman spectrum of pyrobitumen,from the chlorite geothermometer and from measured homogenization temperature of natrolite inclusions are 324-354℃,124-166℃ and 89-196℃,respectively;although vary widely,all the temperatures are obviously higher than the normal geothermal temperature.(3)The positive Eu anomaly of chlorite and barite,and the similar distribution pattern in rare earth elements between natrolite and basalt indicate they are from magmatic hydrothermal fluid.Moreover,drilling data shows that the Kong 2 Member in Well Z56 has several sets of basalt interlayers,suggesting there was geologic base of magmatic hydrothermal fluid activity.The magmatic hydrothermal fluid-rock interaction may be one of the reasons for the abnormal enrichment of zeolite in Kong 2 Member of the Cangdong Sag.

Contrast in Fluid M etallogeny between the Tianmashan Au-S Deposit and the Datuanshan Cu Deposit in Tongling,Anhui Province

A comprehensive contrast of ore-forming geological background and ore-forming fluid features, especially fluid ore-forming processes, has been performed between the Tianmashan and the Datuanshan ore deposits in Tongling, Anhui Province. The major reasons for the formation of the stratabound skarn Au-S ore deposit in Tianmashan and the stratabound skarn Cu ore deposit in Datuanshan are analyzed in accordance with this contrast. The magmatic pluton in Tianmashan is rich in Au and poor in Cu, but that in Datuanshan is rich in Cu and Au. The wallrock strata in Tianmashan contain Au-bearing pyrite layers with some organic substance but those in Datuanshan contain no such layers. Moreover, the ore-forming fluids in Tianmashan are dominantly magmatic ones at the oxide and sulfide stages, but those with high content of Cu in Datuanshan are mainly groundwater fluids. In addition, differences in compositional evolution and physicochemical condition variation of the ore-forming fluids result in gradual dispersion

Relationship between Thermal Metamorphism of Coal and the Periodic Variation Law of Geochemical Behavior of Elements:A Study on the C2 Coal Seam in the Fengfeng Mining Area of the Handan Coalfield in Hebei,China

This study highlights the response of the periodic variation of the geochemical behavior of elements to the thermal metamorphism of coal by considering the differentiation mode and differentiation degree of elements of the C2 coal seam in the Fengfeng mining area of the Handan Coalfield in Hebei,China.The periodic variation of the geochemical behavior of elements was observed to change towards a certain direction as the degree of metamorphism of a geological body increased.Based on the coincidence degree(or similarity degree)between the geochemical behavior of elements and periodic variation of elements,the 57 elements in this study were divided into two levels.The periodic variation of the geochemical behavior of first-level elements was largely synchronous with that of their first ionization energy,suggesting that only one differentiation mode exists and the elements are mainly inorganically associated.The differentiation mode of the second-level elements deviated to a certain extent from their first ionization energy;the larger the deviation,the more complicated and diverse was the differentiation mode.Among the second-level elements,the grade of coal metamorphism has evident and intuitive effects on the proportion of elements with particular structural features,such as the 4q+3 type of elements and the odd-odd elements.In addition,the distribution of elements in organic and inorganic matter within coal are subject to the structural features of the elements.The differentiation mode and differentiation intensity of elements could be characterized by the hierarchical parameter and differentiation intensity.The hierarchical parameter and differentiation intensity of certain elements showed a good positive or negative correlation with R_(max) in coal.The 57 elements in this study were quantitatively ordered according to the degree of magmatic hydrothermal fluid influence and thermal metamorphism of coal through graphs depicting the goodness of fit,correlation coefficient with R_(max),and differentiation intensity.The results of this study are consistent with the results of previous field research,illustrating the scientific significance and application value of this study on the periodic variation of the geochemical behavior of elements.

Characteristic Solutes in Geothermal Water from the Rehai Hydrothermal System,Southwestern China

Rehai, a high-temperature hydrothermal system located in the southern part of the Tengchong volcanic geothermal area of Yunnan Province, is characterized by intensive hydrothermal activities. The hot springs at Rehai that have been sampled so far are Na-HCO3-Cl or Na-HCO3 springs except for the one at Diretiyanqu （experience geothermal area） which is an acid sulfate spring. As typical characteristic solution constituents in high-temperature hydrothermal systems with magma as heat source, CI, B and As in the Rehai geothermal waters originate mainly from the addition of magmatic fluid. However, both the mixing of magmatic fluid and the dissolution of reservoir hostrocks contribute to the enrichment of fluoride in the Rehai geothermal waters, although their fluoride concentrations are primarily controlled by the solubility of fluorite as indicated by a clear negative relation between solution fluoride and calcium concentrations. The much higher concentration of SO4^2- in the Diretiyanqu Spring as compared to the other springs outcropping at Rehai implies a quite different geochemical genesis for this spring. The H2S-rich vapor, separated from the deep geothermal fluid during boiling process （i.e., adiabatic cooling）, can ascend to shallow aquifers where it is mixed with cold groundwaters and oxidized. Acid sulfate-rich hot springs are generally formed in this manner although only one spring of this type has been samnled during the field investigation of this studv.