Using Quantitative Textural Analysis to Understand the Emplacement of Shallow-Level Rhyolitic Laccoliths--a Case Study from the Halle Volcanic Complex, Germany   总被引：3，自引：1，他引：2  

MOCK  A.; JERRAM  D. A.; BREITKREUZ  C. 《Journal of Petrology》2003,44(5):833-849

In qualitatively homogeneous magmatic bodies, quantitative texturalanalysis—such as crystal size distribution, modal abundance,and spatial distribution pattern analyses—allows theirinternal heterogeneity to be measured and interpreted. In thisstudy, these methods are applied to samples from a 300 m drillcore through one of the porphyritic rhyolitic laccoliths (Petersbergunit) of the  相似文献   

Crystal Size Distributions (CSD) in Three Dimensions: Insights from the 3D Reconstruction of a Highly Porphyritic Rhyolite   总被引：7，自引：2，他引：5  

MOCK  A.; JERRAM  D. A. 《Journal of Petrology》2005,46(8):1525-1541

Growth histories and residence times of crystals in magmaticsystems can be revealed by studying crystal sizes, size distributionsand shapes. In this contribution, serial sectioning has beenemployed on a sample of porphyritic rhyolite from a Permo-Carboniferouslaccolith from the Halle Volcanic Complex, Germany, to reconstructthe distribution of felsic phenocrysts in three dimensions inorder to determine their true shapes, sizes and three-dimensionalsize distributions. A model of all three phenocryst phases (quartz,plagioclase, K-feldspar) with 217 crystals, and a larger modelcontaining 1599 K-feldspar crystals was reconstructed in threedimensions. The first model revealed a non-touching frameworkof crystals in three dimensions, suggesting that individualcrystals grew freely in the melt prior to quenching of the texture.However, crystal shapes are complex and show large variationon a Zingg diagram (intermediate over long axis plotted againstshort over intermediate axis). They often do not resemble thecrystallographic shapes expected for phenocrysts growing unhinderedfrom a melt, indicating complex growth histories. In contrast,the three-dimensional size distribution is a simple straightline with a negative slope. Stereologically corrected size distributionsfrom individual sections compare well with stereologically correctedsize distributions obtained previously from the same sample.However, crystal size distribution (CSD) data from individualsections scatter considerably. It is shown that CSDs can berobustly reproduced with a sampling size of greater than 200crystals. The kind of shape assumed in stereological correctionof CSDs, however, has a large influence on the calculation andestimation of crystal residence times. KEY WORDS: 3D reconstruction; crystal shapes; CSD; porphyritic rhyolite; quantitative petrography  相似文献