Formation of a laccolith by magma pulses: Evidence from modal and chemical composition of the 500 m long borehole section through the Permo-Carboniferous Landsberg laccolith (Halle Volcanic Complex)

Abstract

However, chemical variations within the magma body could also be an evidence for fractional crystallization and/or magmatic segregation. Additional information that may help to indicate that internal heterogeneity in the magma body was due to separate magma pulses can be provided by application of quantitative textural analysis including modal abundance of minerals (Mock et al., 2003). In the current paper we use combined chemical and mineralogical analyses of selected samples from the 500 m long completely cored well, which constitutes the upper part of the coarse-grained rhyolitic Landsberg laccolith (Halle Volcanic Complex, Germany). The bottom of the laccolith was not drilled, but the core analysed in this paper probably represents more than half of the vertical section through the laccolith. Our goal is to interpret the modal and chemical variations of the Landsberg

Towards Identification of Zircon Populations in Permo-Carboniferous Rhyolites of Central Europe: Insight from Automated SEM-Mineral Liberation Analyses

“…Zircon in Halle was often associated with other accessory minerals such as apatite, rutile, and Fe-oxide-forming veins that intruded later than the majority of the laccolith body. This would be in accordance with previous interpretations of multiple magmatic injections forming laccolith bodies [15,21,30], and would additionally suggest the presence of strongly differentiated melts during laccolith formation. As such, at least two populations occurred in Halle rhyolite-one in biotite, and one related to this later melt infiltration.…”

“…The Halle Complex comprises several fine-grained and coarse-grained laccoliths [19,20] emplaced from 291.7 ± 1.8 to 301 ± 3 Ma [19]. The individual laccoliths were formed by several successive magma pulses with evidence of the prolonged laccolith formation being consistent with structural, petrological, and geochemical data [15,21,22]. The sample analyzed in this study came from coarse-grained Landsberg laccolith that was shown to contain chemically and isotopically diverse zircon of Permian age, suggesting the presence of both antecrystic and autocrystic grains [23].…”

“…Supplementary Materials: The following are available online at http://www.mdpi.com/2075-163X/10/4/308/s1, Table S1: Reproducibility of whole rock analyses based on duplicate analyses of a single sample and the reference material, accuracy of whole rock analyses based on comparison of RM analyses to the expected value; Table S2: Whole rock analyses from this study and data from References [9,15] used as a reference composition for the rocks analyzed in this study by MLA-SEM; Table S3: Modal composition as analyzed in this study by MLA-SEM; Table S4: Proportions of different minerals associated with zircon as analyzed by MLA-SEM; Table S5: Data for each zircon grain in each sample used for statistical calculations as analyzed in this study by MLA-SEM. No statistical differences were noted for Length/Breadth ratio and angularity.…”

“…Samples from Organy (n = 6), Bieberstein (n = 6), and Krucze (n = 6) were analyzed in Bureau Veritas Commodities Canada Ltd. by ICP-MS. Chemical composition of bulk rock samples from Chemnitz and Halle were taken from the literature (n = 10, n = 22) [9,15]. The precision for major elements was from 0.11% Relative Standard Devation (RSD) for SiO 2 from Organy to 2.44% RSD for TiO 2 from Krucze.…”

“…Dating of this rhyolite will be an analytical challenge, but one that may provide interesting results if the two populations are analyzed separately. Comparison of whole rock SiO 2 and Zr contents in the studied rhyolites (including the whole rock composition published in [9,15] with datasets from Bishop Tuff [35], Taupo Volcanic Zone [43], and Yellowstone [38].…”