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Papers by Michael Marks Marks

Geochmica et Cosmochimica Acta

cspg.org

Summary We present details of a field-based study on the evolution of alkaline to peralkaline roc... more Summary We present details of a field-based study on the evolution of alkaline to peralkaline rocks from the Mont Saint-Hiliaire complex, Quebec, Canada. The progressive magmatic evolution of the complex is represented by three melt batches:(1) primitive ...

Neues Jahrbuch für Mineralogie - Abhandlungen, 2010

ABSTRACT Eudialyte-group minerals (EGM) are typical constituents of agpaitic varieties of peralka... more ABSTRACT Eudialyte-group minerals (EGM) are typical constituents of agpaitic varieties of peralkaline rocks. In their complex structure (N15-16M(1)6M(2)3Z3M(3)M(4)Si24O66-73(OH)0-9X2), many cations (e.g. Na+, Ca2+, Fe2+, Mn2+, REE3+, Zr4+, and Si4+) as well as different hydrogen-bearing species (H2O, OH-, H3O+) may occupy different structural sites. Also, two potentially vacancy bearing positions are present. Thus, various methods of calculation of mineral formulae for EGM in the literature are inconsistent and in some cases not charge-balanced. We present an extended and improved scheme for site assignment using IMA-approved end-members and taking into account the different structural units of EGM. This method is based on electron microprobe analyses alone not considering different valence states of Fe and Mn and undetermined H2O-contents. However, comparison with structural refinement data from the literature reveals major agreement and significant improvement compared to earlier proposed methods. The instruction given here can easily be transferred to a table calculation spread sheet (e.g. EXCEL©), which is available from the corresponding author on request.

Journal of Petrology, 2010

American Mineralogist, 2014

Eur J Mineral, 2001

The layered peralkaline igenous Ilimaussaq complex (Gardar failed-rift province in southwest Gree... more The layered peralkaline igenous Ilimaussaq complex (Gardar failed-rift province in southwest Greenland) has attracted exploration activities in past and present. The intrusion was emplaced in three magmatic phases, evolving in an essentially closed-system. The composition of the rocks covers a broad range of alkaline rocks, ranging from alkaline to peralkaline granites and syenites to highly evolved nepheline syenites. The latest magmatic rocks are among the most differentiated, known on earth [1]. During late-stage magmatic ...

Lithos, 2012

ABSTRACT Sadiman volcano is located in the Crater Highlands area of northern Tanzania, which lies... more ABSTRACT Sadiman volcano is located in the Crater Highlands area of northern Tanzania, which lies next to the western escarpment of the Gregory rift—a part of the eastern branch of the East African Rift system. It consists of inter-layered phonolitic tuffs, tuff breccias (with blocks of nephelinites) and nephelinitic lava flows. Rare xenoliths of phonolite lava and ijolite were observed within the nephelinite lavas with ijolite blocks occurring in pho-nolitic tuffs. No evidence for the presence of melilite-bearing and/or carbonatitic rocks was found during this study. On the basis of petrography, mineralogy and geochemistry the nephelinites are divided into highly porphyritic nephelinite, wollastonite nephelinite and phonolitic nephelinite, the latter of which is the dominant variety at Sadiman. Nepheline + clinopyroxene + titanite ± perovskite ± andradite–schorlomite ± wollastonite ± sanidine ± sodalite are the principle pheno-and microphenocryst phases. The nephelinites are highly evolved (Mg# = 0.17–0.26) alkaline to peralkaline (AI = 0.88–1.21) rocks enriched in incompati-ble elements such as Rb, Ba, Th, U, Nb, Pb, Ta, Sr and light REEs, and strongly depleted in P and Ti. This sug-gests derivation from an enriched mantle source and fractionation of apatite and Ti-rich mineral(s). Primary melt inclusions in nepheline phenocrysts (T homogenization = 860–1100 °C) indicate enrichment of volatile components in the melts, particularly of fluorine (up to 1.8 wt.% in silicate glass) resulting in the formation of daughter fluorite in partly and complete crystallized inclusions. The Sadiman nephelinites crystallized under relatively oxidizing conditions (above the FMQ buffer), which differ from the reducing conditions reported for trachytic and pantelleritic rocks from other parts of the Gregory rift. Similar rock types and rel-atively oxidizing conditions are known from Oldoinyo Lengai and other localities, all of which are closely associated with carbonatites. By analogy, we conclude that andradite–schorlomite-rich nephelinites may in-dicate a pre-stage on the evolutionary path towards carbonatitic magmatism.

Journal of Petrology, 2008

Journal of Petrology, 2003

Lithos, 2012

ABSTRACT Sadiman volcano is located in the Crater Highlands area of northern Tanzania, which lies... more ABSTRACT Sadiman volcano is located in the Crater Highlands area of northern Tanzania, which lies next to the western escarpment of the Gregory rift—a part of the eastern branch of the East African Rift system. It consists of inter-layered phonolitic tuffs, tuff breccias (with blocks of nephelinites) and nephelinitic lava flows. Rare xenoliths of phonolite lava and ijolite were observed within the nephelinite lavas with ijolite blocks occurring in pho-nolitic tuffs. No evidence for the presence of melilite-bearing and/or carbonatitic rocks was found during this study. On the basis of petrography, mineralogy and geochemistry the nephelinites are divided into highly porphyritic nephelinite, wollastonite nephelinite and phonolitic nephelinite, the latter of which is the dominant variety at Sadiman. Nepheline + clinopyroxene + titanite ± perovskite ± andradite–schorlomite ± wollastonite ± sanidine ± sodalite are the principle pheno-and microphenocryst phases. The nephelinites are highly evolved (Mg# = 0.17–0.26) alkaline to peralkaline (AI = 0.88–1.21) rocks enriched in incompati-ble elements such as Rb, Ba, Th, U, Nb, Pb, Ta, Sr and light REEs, and strongly depleted in P and Ti. This sug-gests derivation from an enriched mantle source and fractionation of apatite and Ti-rich mineral(s). Primary melt inclusions in nepheline phenocrysts (T homogenization = 860–1100 °C) indicate enrichment of volatile components in the melts, particularly of fluorine (up to 1.8 wt.% in silicate glass) resulting in the formation of daughter fluorite in partly and complete crystallized inclusions. The Sadiman nephelinites crystallized under relatively oxidizing conditions (above the FMQ buffer), which differ from the reducing conditions reported for trachytic and pantelleritic rocks from other parts of the Gregory rift. Similar rock types and rel-atively oxidizing conditions are known from Oldoinyo Lengai and other localities, all of which are closely associated with carbonatites. By analogy, we conclude that andradite–schorlomite-rich nephelinites may in-dicate a pre-stage on the evolutionary path towards carbonatitic magmatism.

Chemical Geology

Apatite is ubiquitous in a wide range of magmatic rocks and its F–Cl–Br–S systematics can be used... more Apatite is ubiquitous in a wide range of magmatic rocks and its F–Cl–Br–S systematics can be used to decipher e.g., mixing processes within a magmatic complex and may give insights into fluid un-mixing and degassing processes during the emplacement and cooling of plutonic rocks.In this study, we analyzed a F-apatite (Durango, Mexico), a Cl-apatite (Ødegården, Norway) and apatites from five plutonic samples from the alkaline Mt. Saint Hilaire Complex (Canada) by means of Electron Microprobe Analysis (EPMA), Laser Ablation ICP-MS (LA-ICP-MS), Secondary Ion Mass Spectrometry (SIMS), pyrohydrolysis combined with ion chromatography, Fourier Transformed Infrared Spectroscopy (FTIR), Instrumental Neutron Activation Analysis (INAA) and Total Reflection X-ray Fluorescence Analysis (TXRF).The special focus of our study is Br, since the analytical possibilities for this element are especially in the low- to sub-μg/g range restricted and thus, reliable concentration data for Br in rock-forming minerals are scarce. We demonstrate here that TXRF, which is barely used in geosciences so far, is suitable for analyzing the bulk content of Br and Cl as well as of a range of important trace metals (e.g., Sr, Ce, Fe, Mn, As) in apatite simultaneously. The TXRF method combines the advantages of low to very low detection limits (μg/g- to sub-μg/g range), small sample amounts needed (mg range) and a relatively fast and inexpensive analytical procedure. Depending on the As content of apatite, reliable concentration data for Br can be produced with detection limits as low as 0.2 μg/g.Using the Durango apatite as an internal reference material, SIMS analyses give consistent results with EPMA, INAA and TXRF and allow for detailed insights into the F–Cl–Br–S systematics of apatites. The presented data set reveals significant heterogeneities within and between different apatite grains from a single sample.► Br concentrations for magmatic minerals are scarce. ► TXRF can be used to analyze the bulk Br content in apatite. ► A Br concentration of around 0.1 μg/g for the Durango apatite is proposed.

Geochmica et Cosmochimica Acta

cspg.org

Summary We present details of a field-based study on the evolution of alkaline to peralkaline roc... more Summary We present details of a field-based study on the evolution of alkaline to peralkaline rocks from the Mont Saint-Hiliaire complex, Quebec, Canada. The progressive magmatic evolution of the complex is represented by three melt batches:(1) primitive ...

Neues Jahrbuch für Mineralogie - Abhandlungen, 2010

ABSTRACT Eudialyte-group minerals (EGM) are typical constituents of agpaitic varieties of peralka... more ABSTRACT Eudialyte-group minerals (EGM) are typical constituents of agpaitic varieties of peralkaline rocks. In their complex structure (N15-16M(1)6M(2)3Z3M(3)M(4)Si24O66-73(OH)0-9X2), many cations (e.g. Na+, Ca2+, Fe2+, Mn2+, REE3+, Zr4+, and Si4+) as well as different hydrogen-bearing species (H2O, OH-, H3O+) may occupy different structural sites. Also, two potentially vacancy bearing positions are present. Thus, various methods of calculation of mineral formulae for EGM in the literature are inconsistent and in some cases not charge-balanced. We present an extended and improved scheme for site assignment using IMA-approved end-members and taking into account the different structural units of EGM. This method is based on electron microprobe analyses alone not considering different valence states of Fe and Mn and undetermined H2O-contents. However, comparison with structural refinement data from the literature reveals major agreement and significant improvement compared to earlier proposed methods. The instruction given here can easily be transferred to a table calculation spread sheet (e.g. EXCEL©), which is available from the corresponding author on request.

Journal of Petrology, 2010

American Mineralogist, 2014

Eur J Mineral, 2001

The layered peralkaline igenous Ilimaussaq complex (Gardar failed-rift province in southwest Gree... more The layered peralkaline igenous Ilimaussaq complex (Gardar failed-rift province in southwest Greenland) has attracted exploration activities in past and present. The intrusion was emplaced in three magmatic phases, evolving in an essentially closed-system. The composition of the rocks covers a broad range of alkaline rocks, ranging from alkaline to peralkaline granites and syenites to highly evolved nepheline syenites. The latest magmatic rocks are among the most differentiated, known on earth [1]. During late-stage magmatic ...

Lithos, 2012

ABSTRACT Sadiman volcano is located in the Crater Highlands area of northern Tanzania, which lies... more ABSTRACT Sadiman volcano is located in the Crater Highlands area of northern Tanzania, which lies next to the western escarpment of the Gregory rift—a part of the eastern branch of the East African Rift system. It consists of inter-layered phonolitic tuffs, tuff breccias (with blocks of nephelinites) and nephelinitic lava flows. Rare xenoliths of phonolite lava and ijolite were observed within the nephelinite lavas with ijolite blocks occurring in pho-nolitic tuffs. No evidence for the presence of melilite-bearing and/or carbonatitic rocks was found during this study. On the basis of petrography, mineralogy and geochemistry the nephelinites are divided into highly porphyritic nephelinite, wollastonite nephelinite and phonolitic nephelinite, the latter of which is the dominant variety at Sadiman. Nepheline + clinopyroxene + titanite ± perovskite ± andradite–schorlomite ± wollastonite ± sanidine ± sodalite are the principle pheno-and microphenocryst phases. The nephelinites are highly evolved (Mg# = 0.17–0.26) alkaline to peralkaline (AI = 0.88–1.21) rocks enriched in incompati-ble elements such as Rb, Ba, Th, U, Nb, Pb, Ta, Sr and light REEs, and strongly depleted in P and Ti. This sug-gests derivation from an enriched mantle source and fractionation of apatite and Ti-rich mineral(s). Primary melt inclusions in nepheline phenocrysts (T homogenization = 860–1100 °C) indicate enrichment of volatile components in the melts, particularly of fluorine (up to 1.8 wt.% in silicate glass) resulting in the formation of daughter fluorite in partly and complete crystallized inclusions. The Sadiman nephelinites crystallized under relatively oxidizing conditions (above the FMQ buffer), which differ from the reducing conditions reported for trachytic and pantelleritic rocks from other parts of the Gregory rift. Similar rock types and rel-atively oxidizing conditions are known from Oldoinyo Lengai and other localities, all of which are closely associated with carbonatites. By analogy, we conclude that andradite–schorlomite-rich nephelinites may in-dicate a pre-stage on the evolutionary path towards carbonatitic magmatism.

Journal of Petrology, 2008

Journal of Petrology, 2003

Lithos, 2012

ABSTRACT Sadiman volcano is located in the Crater Highlands area of northern Tanzania, which lies... more ABSTRACT Sadiman volcano is located in the Crater Highlands area of northern Tanzania, which lies next to the western escarpment of the Gregory rift—a part of the eastern branch of the East African Rift system. It consists of inter-layered phonolitic tuffs, tuff breccias (with blocks of nephelinites) and nephelinitic lava flows. Rare xenoliths of phonolite lava and ijolite were observed within the nephelinite lavas with ijolite blocks occurring in pho-nolitic tuffs. No evidence for the presence of melilite-bearing and/or carbonatitic rocks was found during this study. On the basis of petrography, mineralogy and geochemistry the nephelinites are divided into highly porphyritic nephelinite, wollastonite nephelinite and phonolitic nephelinite, the latter of which is the dominant variety at Sadiman. Nepheline + clinopyroxene + titanite ± perovskite ± andradite–schorlomite ± wollastonite ± sanidine ± sodalite are the principle pheno-and microphenocryst phases. The nephelinites are highly evolved (Mg# = 0.17–0.26) alkaline to peralkaline (AI = 0.88–1.21) rocks enriched in incompati-ble elements such as Rb, Ba, Th, U, Nb, Pb, Ta, Sr and light REEs, and strongly depleted in P and Ti. This sug-gests derivation from an enriched mantle source and fractionation of apatite and Ti-rich mineral(s). Primary melt inclusions in nepheline phenocrysts (T homogenization = 860–1100 °C) indicate enrichment of volatile components in the melts, particularly of fluorine (up to 1.8 wt.% in silicate glass) resulting in the formation of daughter fluorite in partly and complete crystallized inclusions. The Sadiman nephelinites crystallized under relatively oxidizing conditions (above the FMQ buffer), which differ from the reducing conditions reported for trachytic and pantelleritic rocks from other parts of the Gregory rift. Similar rock types and rel-atively oxidizing conditions are known from Oldoinyo Lengai and other localities, all of which are closely associated with carbonatites. By analogy, we conclude that andradite–schorlomite-rich nephelinites may in-dicate a pre-stage on the evolutionary path towards carbonatitic magmatism.

Chemical Geology

Apatite is ubiquitous in a wide range of magmatic rocks and its F–Cl–Br–S systematics can be used... more Apatite is ubiquitous in a wide range of magmatic rocks and its F–Cl–Br–S systematics can be used to decipher e.g., mixing processes within a magmatic complex and may give insights into fluid un-mixing and degassing processes during the emplacement and cooling of plutonic rocks.In this study, we analyzed a F-apatite (Durango, Mexico), a Cl-apatite (Ødegården, Norway) and apatites from five plutonic samples from the alkaline Mt. Saint Hilaire Complex (Canada) by means of Electron Microprobe Analysis (EPMA), Laser Ablation ICP-MS (LA-ICP-MS), Secondary Ion Mass Spectrometry (SIMS), pyrohydrolysis combined with ion chromatography, Fourier Transformed Infrared Spectroscopy (FTIR), Instrumental Neutron Activation Analysis (INAA) and Total Reflection X-ray Fluorescence Analysis (TXRF).The special focus of our study is Br, since the analytical possibilities for this element are especially in the low- to sub-μg/g range restricted and thus, reliable concentration data for Br in rock-forming minerals are scarce. We demonstrate here that TXRF, which is barely used in geosciences so far, is suitable for analyzing the bulk content of Br and Cl as well as of a range of important trace metals (e.g., Sr, Ce, Fe, Mn, As) in apatite simultaneously. The TXRF method combines the advantages of low to very low detection limits (μg/g- to sub-μg/g range), small sample amounts needed (mg range) and a relatively fast and inexpensive analytical procedure. Depending on the As content of apatite, reliable concentration data for Br can be produced with detection limits as low as 0.2 μg/g.Using the Durango apatite as an internal reference material, SIMS analyses give consistent results with EPMA, INAA and TXRF and allow for detailed insights into the F–Cl–Br–S systematics of apatites. The presented data set reveals significant heterogeneities within and between different apatite grains from a single sample.► Br concentrations for magmatic minerals are scarce. ► TXRF can be used to analyze the bulk Br content in apatite. ► A Br concentration of around 0.1 μg/g for the Durango apatite is proposed.