Hydrogen isotopic compositions of pyroxenes in peridotite xenoliths from the Nushan volcano, Anhui Province, SE China have been obtained using an ion probe (Cameca 1270). D/H ratios are constant within a single grain ...Hydrogen isotopic compositions of pyroxenes in peridotite xenoliths from the Nushan volcano, Anhui Province, SE China have been obtained using an ion probe (Cameca 1270). D/H ratios are constant within a single grain and among the different grains from the same sample. The lack of correlation between the D/H ratios and the hydrogen contents indicates that the hydrogen isotopic compositions are inherited from their mantle source. Combining with the δD values of coexisting amphiboles, it is inferred that the Nushan mantle experienced at least a two-stage metasomatic event. One was responsible for formation of amphiboles with extremely variable δD values, and the other was probably responsible for the high δD values (up to ?20‰) of some clinopyroxenes from peridotites, clinopyroxene and mica megacrysts. High δD values point to a subduction-related fluid being involved in one metasomatic event. The primary δD values (?90‰ to ?140‰) of the Nushan pyroxenes, together with data gleaned from the literature, suggest that the D/H ratios of the nominally anhydrous mineral reservoir might have differed from that of the other mantle hydrogen in being relatively depleted in D.展开更多
In order to derive the distribution of olivine and pyroxene in Crater Copernicus, we compute two band ratios （950/750 and 2 000/1 500 nm）, percent content of elements （Ai%, Ca%, Mg%, FeO%） and maturity （Is/FeO） ...In order to derive the distribution of olivine and pyroxene in Crater Copernicus, we compute two band ratios （950/750 and 2 000/1 500 nm）, percent content of elements （Ai%, Ca%, Mg%, FeO%） and maturity （Is/FeO） based on Clementine UVVIS and NIR image data. The central peaks of Copernicus, which are known to be olivine-rich or pyroxene-rich, are chosen as ＂ground truth＂ and ROIs used to derive the distribution of olivine and pyroxene with a decision tree and spectral angle mapper （SAM）. Additionally, we compared previous works and the extraction results coming from the decision tree and the SAM method. The extraction of olivine by both decision tree and SAM agrees well with the previous works＇ descriptions, and the result by SAM is more accurate than that by decision tree because spectral features are fully used in SAM. For pyroxene extraction, there is a difference between SAM and the decision tree; one of the reasons is that the decision tree does not fully take advantage of spectral features but is only based on statistics. SAM uses band indices that can be easily extended to other areas on the Moon.展开更多
In this paper, tectonic and geothermobarometric environments have been studied with respect to the combination of pyroxene, olivine and plagioclase in volcanic rocks in the southeast of Bam. The combination of volcani...In this paper, tectonic and geothermobarometric environments have been studied with respect to the combination of pyroxene, olivine and plagioclase in volcanic rocks in the southeast of Bam. The combination of volcanic rocks in the region consists of olivine basalt, basalt, alkaline basalt, andesite, trachyandesite and pyroxene andesite. This combination is the result of the processes of crystallization and sometimes contamination. Plagioclase, clinopyroxene, olivine, and amphibole constitute the major minerals (rock forming minerals) in these rocks. Porphyritic to mega-porphyritic textures with microlithic, glumero-porphyritic and amigdaluidal matrix are observed. Based on the thermometric calculations, plagioclase, pyroxene, and olivine minerals and the rocks of this region are crystallized at a pressure of 1.5 to 7 kb and temperatures ranging from about 700°C to 1250°C.展开更多
基金supported by the National Natural Science Foundation of China(Grants 49803002 and 40473007)Program for New Century Excellent Talents in University(NCET)the CAS-CNRS-CNR cooperative project.
文摘Hydrogen isotopic compositions of pyroxenes in peridotite xenoliths from the Nushan volcano, Anhui Province, SE China have been obtained using an ion probe (Cameca 1270). D/H ratios are constant within a single grain and among the different grains from the same sample. The lack of correlation between the D/H ratios and the hydrogen contents indicates that the hydrogen isotopic compositions are inherited from their mantle source. Combining with the δD values of coexisting amphiboles, it is inferred that the Nushan mantle experienced at least a two-stage metasomatic event. One was responsible for formation of amphiboles with extremely variable δD values, and the other was probably responsible for the high δD values (up to ?20‰) of some clinopyroxenes from peridotites, clinopyroxene and mica megacrysts. High δD values point to a subduction-related fluid being involved in one metasomatic event. The primary δD values (?90‰ to ?140‰) of the Nushan pyroxenes, together with data gleaned from the literature, suggest that the D/H ratios of the nominally anhydrous mineral reservoir might have differed from that of the other mantle hydrogen in being relatively depleted in D.
基金supported by the Research Foundation of Science and Technology, China University of Geosciences (Wuhan)the Fundamental Research Funds for the Central Universities (No. 2010119047)
文摘In order to derive the distribution of olivine and pyroxene in Crater Copernicus, we compute two band ratios （950/750 and 2 000/1 500 nm）, percent content of elements （Ai%, Ca%, Mg%, FeO%） and maturity （Is/FeO） based on Clementine UVVIS and NIR image data. The central peaks of Copernicus, which are known to be olivine-rich or pyroxene-rich, are chosen as ＂ground truth＂ and ROIs used to derive the distribution of olivine and pyroxene with a decision tree and spectral angle mapper （SAM）. Additionally, we compared previous works and the extraction results coming from the decision tree and the SAM method. The extraction of olivine by both decision tree and SAM agrees well with the previous works＇ descriptions, and the result by SAM is more accurate than that by decision tree because spectral features are fully used in SAM. For pyroxene extraction, there is a difference between SAM and the decision tree; one of the reasons is that the decision tree does not fully take advantage of spectral features but is only based on statistics. SAM uses band indices that can be easily extended to other areas on the Moon.
文摘In this paper, tectonic and geothermobarometric environments have been studied with respect to the combination of pyroxene, olivine and plagioclase in volcanic rocks in the southeast of Bam. The combination of volcanic rocks in the region consists of olivine basalt, basalt, alkaline basalt, andesite, trachyandesite and pyroxene andesite. This combination is the result of the processes of crystallization and sometimes contamination. Plagioclase, clinopyroxene, olivine, and amphibole constitute the major minerals (rock forming minerals) in these rocks. Porphyritic to mega-porphyritic textures with microlithic, glumero-porphyritic and amigdaluidal matrix are observed. Based on the thermometric calculations, plagioclase, pyroxene, and olivine minerals and the rocks of this region are crystallized at a pressure of 1.5 to 7 kb and temperatures ranging from about 700°C to 1250°C.
