Eight dissolution models of calcium apatites(both fluorapatite and hydroxyapatite) in acids were drawn from the published literature,analyzed and discussed.Major limitations and drawbacks of the models were conversed ...Eight dissolution models of calcium apatites(both fluorapatite and hydroxyapatite) in acids were drawn from the published literature,analyzed and discussed.Major limitations and drawbacks of the models were conversed in details.The models were shown to deal with different aspects of apatite dissolution phenomenon and none of them was able to describe the dissolution process in general.Therefore,an attempt to combine the findings obtained by different researchers was performed which resulted in creation of the general description of apatite dissolution in acids.For this purpose,eight dissolution models were assumed to complement each other and provide the correct description of the specific aspects of apatite dissolution.The general description considers all possible dissolution stages involved and points out to some missing and unclear phenomena to be experimentally studied and verified in future.This creates a new methodological approach to investigate reaction mechanisms based on sets of affine data,obtained by various research groups under dissimilar experimental conditions.展开更多
Apatites occurring in sedimentary rocks are carbonate fluorapatites (C-F apatites) with differentCO_2 contents. During diagenesis. the CO_2 in the C-F apatites gradually decreased with the increasing strengthof diagen...Apatites occurring in sedimentary rocks are carbonate fluorapatites (C-F apatites) with differentCO_2 contents. During diagenesis. the CO_2 in the C-F apatites gradually decreased with the increasing strengthof diagenesis. resulting in the systematic changes in refractive index. specific gravity, cell parameters and crystalchemistry of apatites. On the basis of X-ray diffraction and IR spectroscopic analyses, the author proposes twoparameters for determining diagenetic stages. i.e.. the crystallinity index (CR) and sharpness index (SH). Thesetwo parameters serve as new criteria for the determination. which due to the common existence of phosphorousnodules and bands and argillo-crystalline cement in sedimentary rocks, most likely have wide prospects for ap-plication.展开更多
1 Introduction Studies of marine sedimentary phosphate rock have lasted decades,scholars proposed some standpoints about mineralization,however,the genesis of mineral deposits remains to be a controversial question(Sh...1 Introduction Studies of marine sedimentary phosphate rock have lasted decades,scholars proposed some standpoints about mineralization,however,the genesis of mineral deposits remains to be a controversial question(She et al.,2013).There are many viewpoints of mineralization about the Doushantuo phosphorites,Central Guizhou,including biological mineralization(Mi et al.,2010;Shi et al.,2005),展开更多
文摘Eight dissolution models of calcium apatites(both fluorapatite and hydroxyapatite) in acids were drawn from the published literature,analyzed and discussed.Major limitations and drawbacks of the models were conversed in details.The models were shown to deal with different aspects of apatite dissolution phenomenon and none of them was able to describe the dissolution process in general.Therefore,an attempt to combine the findings obtained by different researchers was performed which resulted in creation of the general description of apatite dissolution in acids.For this purpose,eight dissolution models were assumed to complement each other and provide the correct description of the specific aspects of apatite dissolution.The general description considers all possible dissolution stages involved and points out to some missing and unclear phenomena to be experimentally studied and verified in future.This creates a new methodological approach to investigate reaction mechanisms based on sets of affine data,obtained by various research groups under dissimilar experimental conditions.
文摘Apatites occurring in sedimentary rocks are carbonate fluorapatites (C-F apatites) with differentCO_2 contents. During diagenesis. the CO_2 in the C-F apatites gradually decreased with the increasing strengthof diagenesis. resulting in the systematic changes in refractive index. specific gravity, cell parameters and crystalchemistry of apatites. On the basis of X-ray diffraction and IR spectroscopic analyses, the author proposes twoparameters for determining diagenetic stages. i.e.. the crystallinity index (CR) and sharpness index (SH). Thesetwo parameters serve as new criteria for the determination. which due to the common existence of phosphorousnodules and bands and argillo-crystalline cement in sedimentary rocks, most likely have wide prospects for ap-plication.
文摘1 Introduction Studies of marine sedimentary phosphate rock have lasted decades,scholars proposed some standpoints about mineralization,however,the genesis of mineral deposits remains to be a controversial question(She et al.,2013).There are many viewpoints of mineralization about the Doushantuo phosphorites,Central Guizhou,including biological mineralization(Mi et al.,2010;Shi et al.,2005),
