Existing studies provide adequate petrological evidences on ca.500 Ma ultra-high pressure(UHP)metamorphism in the North Qinling Orogenic Belt(NQOB)in central China,but the genesis of 470-420 Ma multi-phase granulite-f...
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Existing studies provide adequate petrological evidences on ca.500 Ma ultra-high pressure(UHP)metamorphism in the North Qinling Orogenic Belt(NQOB)in central China,but the genesis of 470-420 Ma multi-phase granulite-facies metamorphism in the NQOB and their relationship with the ca.500 Ma UHP metamorphism remain controversial,resulting in the early Paleozoic evolution of the Qinling Orogenic Belt(QOB)highly *** this study,we present mafic granulites and host felsic gneisses with a“red-eye socket”texture from the Shuanglong area,eastern NQOB,which recorded two phases of granulite-facies metamorphism superimposing on former eclogite-facies *** former eclogite-facies metamorphism is indicated by eclogite-facies zircon trace element patterns and 496-495 Ma zircon ages,which are the same with those of the HP-UHP eclogite-facies metamorphic rocks in *** first granulite-facies metamorphism occurred at 460-448 Ma is characterized by coarse-grained minerals in *** and zonings of these minerals define an anticlockwise P-T path involving a prograde stage(751-763℃),a high-temperature peak stage(9.2 kbar and 864℃),and a near-isobaric cooling retrograde stage(8.3 kbar and 818℃).The second granulite-facies metamorphism occurred at 422-421 Ma is represented by coronal garnet and coexisting fine-grained mineral *** garnet compositional zonings suggest a clockwise P-T path consisting of a high-pressure peak stage(9.5-11.2 kbar and 748-783℃)and a decompressing and heating retrograde stage(9.2-9.5 kbar and 789-800℃).Combining dating results of leucosomes in these rocks and existing data,we proposed a new model for early Paleozoic tectonic evolution of the *** North Qinling Terrane(NQT),probably separated from the South China Block(SCB)during the breakup of Rodinia,drifted northwards and underwent UHP metamorphism at 500 Ma and then rapidly exhumed to crust ***,the Shangdan Ocean subducted northwards beneath the exhu
Becausemining complete set of frequent patterns from dense database could be impractical, an interesting alternative has been proposed recently. Instead of mining the complete set of frequent patterns, the new model o...
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Becausemining complete set of frequent patterns from dense database could be impractical, an interesting alternative has been proposed recently. Instead of mining the complete set of frequent patterns, the new model only finds out the maximal frequent patterns, which can generate all frequent patterns. FP-growth algorithm is one of the most efficient frequent-pattern mining methods published so far. However,because FP-tree and conditional FP-trees must be two-way traversable, a great deal memory is needed in process of mining. This paper proposes an efficient algorithm Unid_FP-Max for mining maximal frequent patterns based on unidirectional FP-tree. Because of generation method of unidirectional FP-tree and conditional unidirectional FP-trees, the algorithm reduces the space consumption to the fullest extent. With the development of two techniques:single path pruning and header table pruning which can cut down many conditional unidirectional FP-trees generated recursively in mining process, Unid_ FP-Max further lowers the expense of time and space.
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