From a compilation of geochemical data for the discrimination of the tectonic settings of mid-ocean ridge(MOR;3730 samples)and oceanic plateau(OP;3656 samples),we present two new discriminant functions and diagrams ob...From a compilation of geochemical data for the discrimination of the tectonic settings of mid-ocean ridge(MOR;3730 samples)and oceanic plateau(OP;3656 samples),we present two new discriminant functions and diagrams obtained from censored multivariate discordant outlier-free datasets.Ten different sets of data(original concentrations as well as isometric log-ratio transformed(ilr)variables;all 10 major(M)elements as well as all 10 major and 6 trace elements MT)were used to evaluate the quality of discrimination from linear discriminant analysis(LDA)and canonical analysis.Two selected multidimensional models ilrM(9 ilr transformed variables of multi-normally distributed 10 major elements)and ilrMT(15 ilr transformed variables of multi-normally distributed combined 10 major and 6 trace elements),considered as the best or most representative(total of5650 samples for ilrM and 2858 for ilrMT),provided percent success values,respectively,of 80.9%for the MOR and 81.1%for the OP(ilrM)and 88.5%for the MOR and 90.1%for the OP(ilrMT).Both processes(log-ratio transformation and multi-normality)rendered the percent success values similar for both groups(MOR and OP).The respective discriminant functions were successfully used for four tests from known tectonic settings and four application cases(two for ophiolites and two for Precambrian rocks),documenting thus the utility of the new discrimination procedure for the MOR and OP tectonic settings.Furthermore,we showed that our multidimensional procedure is robust against analytical errors or uncertainties,as well as post-emplacement compositional changes caused by element mobility from both low or high temperature alteration.The robustness against the gain or loss of a single element at a time was also documented,from which the ilrMT model was evaluated as more robust than the ilrM model.A new online computer program MOROPdisc was written in Java Framework ZK,which is freely available for use at our web portal http://tlaloc.ier.unam.mx.展开更多
We review the most important computer programs for the classification of igneous rocks and point out those that follow the recommendations of the International Union of Geological Sciences(IUGS).A new program“Igneous...We review the most important computer programs for the classification of igneous rocks and point out those that follow the recommendations of the International Union of Geological Sciences(IUGS).A new program“Igneous Rock Classification System”(IgRoCS),written in Visual Basic,is then described in detail.IgRoCS allows the user to follow strictly the IUGS classification and nomenclature scheme for igneous rocks.The special rocks are first classified,then plutonic rocks are named after the IUGS mineralogical classification,next high-Mg and picritic volcanic rocks are identified from the IUGS criteria,and finally other volcanic rocks are classified according to the TAS diagram and CIPW norm.The chemical classification of volcanic rocks can also be achieved directly without going through the classification of other rock types.The IgRoCS program incorporates the revised standard igneous norm.Thus,the use of this new software is encouraged for a strict application of the IUGS recommendations for igneous rock classification and nomenclature.展开更多
To fill the gap of the nomenclature of altered igneous rocks,a new exhaustive multidimensional classification scheme consistent with the International Union of Geological Sciences(IUGS)is proposed.Our procedure is bas...To fill the gap of the nomenclature of altered igneous rocks,a new exhaustive multidimensional classification scheme consistent with the International Union of Geological Sciences(IUGS)is proposed.Our procedure is based on an extensive database of major element compositions of a total of 32948 relatively fresh rock samples.展开更多
文摘From a compilation of geochemical data for the discrimination of the tectonic settings of mid-ocean ridge(MOR;3730 samples)and oceanic plateau(OP;3656 samples),we present two new discriminant functions and diagrams obtained from censored multivariate discordant outlier-free datasets.Ten different sets of data(original concentrations as well as isometric log-ratio transformed(ilr)variables;all 10 major(M)elements as well as all 10 major and 6 trace elements MT)were used to evaluate the quality of discrimination from linear discriminant analysis(LDA)and canonical analysis.Two selected multidimensional models ilrM(9 ilr transformed variables of multi-normally distributed 10 major elements)and ilrMT(15 ilr transformed variables of multi-normally distributed combined 10 major and 6 trace elements),considered as the best or most representative(total of5650 samples for ilrM and 2858 for ilrMT),provided percent success values,respectively,of 80.9%for the MOR and 81.1%for the OP(ilrM)and 88.5%for the MOR and 90.1%for the OP(ilrMT).Both processes(log-ratio transformation and multi-normality)rendered the percent success values similar for both groups(MOR and OP).The respective discriminant functions were successfully used for four tests from known tectonic settings and four application cases(two for ophiolites and two for Precambrian rocks),documenting thus the utility of the new discrimination procedure for the MOR and OP tectonic settings.Furthermore,we showed that our multidimensional procedure is robust against analytical errors or uncertainties,as well as post-emplacement compositional changes caused by element mobility from both low or high temperature alteration.The robustness against the gain or loss of a single element at a time was also documented,from which the ilrMT model was evaluated as more robust than the ilrM model.A new online computer program MOROPdisc was written in Java Framework ZK,which is freely available for use at our web portal http://tlaloc.ier.unam.mx.
文摘We review the most important computer programs for the classification of igneous rocks and point out those that follow the recommendations of the International Union of Geological Sciences(IUGS).A new program“Igneous Rock Classification System”(IgRoCS),written in Visual Basic,is then described in detail.IgRoCS allows the user to follow strictly the IUGS classification and nomenclature scheme for igneous rocks.The special rocks are first classified,then plutonic rocks are named after the IUGS mineralogical classification,next high-Mg and picritic volcanic rocks are identified from the IUGS criteria,and finally other volcanic rocks are classified according to the TAS diagram and CIPW norm.The chemical classification of volcanic rocks can also be achieved directly without going through the classification of other rock types.The IgRoCS program incorporates the revised standard igneous norm.Thus,the use of this new software is encouraged for a strict application of the IUGS recommendations for igneous rock classification and nomenclature.
基金funded by DGAPA-PAPIIT grant IN100816 and IER-UNAM internal grant to the first author.
文摘To fill the gap of the nomenclature of altered igneous rocks,a new exhaustive multidimensional classification scheme consistent with the International Union of Geological Sciences(IUGS)is proposed.Our procedure is based on an extensive database of major element compositions of a total of 32948 relatively fresh rock samples.
