Mineralogical evidence for the derivation of metaluminous,potassic rocks from peralkaline precursors: The Cordon Syenite Complex (Philippines)     

U. Knittel  A. Cundari 《Mineralogy and Petrology》1990,41(2-4):163-183

Summary Rocks from the Cordon Syenite Complex, located in the Philippine island arc, correspond to miaskitic (metaluminous) potassic lavas from the Roman Region and the Indonesian arc in terms of bulk rock chemistry. However, the mineral chemistry indicates a complex history of multiple equilibrations with liquids of different nature. T-site (Si + Al) occupancy in some clinopyroxenes and Ca contents of alkali feldspar phenocrysts indicate that these phases crystallized under the temperature-pressure subvolcanic regime from host liquids with progressively decreasing (Na + K)/Al ratio. In contrast to current views on the genesis of potassic rocks, it is suggested that differentiated leucite tephrite suites may be derived from peralkaline liquids by alkali loss. Magmas with affinities to lamproites may occur in the Philippine island arc, but a direct genetic relationship between subduction and alkaline/peralkaline magmatism remains questionable.

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Mineralogische Hinweise auf die Entstehung subalkalischer, K-reicher gesteine aus, peralkalischen Vorläufern: Der Syenit Komplex von Cordon (Philippinen)

Zusammenfassung Die Magmatite des im philippinischen Inselbogen gelegenen Syenitkomplexes von Cordon entsprechen in ihrem Gesamtgesteinschemismus den miaskitischen, K-reichen Vul kaniten der Romanischen Provinz und des indonesischen Inselbogens. Die chemische Zusammensetzung einzelner Mineralphasen deutet auf eine komplexere Genese unter Beteiligung von Magmen unterschiedlicher Alkalinität hin. Die Variation in der Besetzung der T-Position (Si + Al) in Klinopyroxenen und der Ca-Gehalte in Alkalifeldspäten wird dahingehend interpretiert, daß diese Phasen unter subvulkanischen Bedingungen aus Schmelzen mit abnehmenden (Na + K)/Al-Verhältnissen kristallisierten. Im Gegensatz zu gängigen Auffassungen wird daher angenommen, daß differenzierte Leucit-Tephrite aus mild-peralkalischen Magman hervorgehen können. Obwohl die K-reichen Magmatite des Syenitkomplexes von Cordon in einem Inselbogen gebildet wurden, ist ein direkter Zusammenhang mit Anreicherungsvorgängen im Bereich der Subduktionszone fraglich.

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Paper presented at the General Assembly of the International Association of Volcanology and Chemistry of the Earth Interior, Santa Fe, New Mexico, 1989.

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Uvarovite: Stability of uvarovite-andradite solid solutions at low pressure     

H. G. Huckenholz  D. Knittel 《Contributions to Mineralogy and Petrology》1976,56(1):61-76

Uvarovite (Ca₃Cr₂Si₃O₁₂) forms a complete solid solution series with andradite (Ca₃Fe ₂ ⁺³ Si₃O₁₂) below 1,137±5 ° C at a total pressure of 1 atm. Pure uvarovite decomposes to pseudowollastonite (CaSiO₃)+eskolaite (Cr₂O₃) at 1,385 ± 10 ° C. The incorporation of Ca₃Fe ₂ ⁺³ Si₃O₁₂ component in the uvarovite structure lowers the thermal stability of the garnet. The breakdown assemblage is garnet_ss (Ca₃(Cr,Fe⁺³ ₂)Si₃O₁₂)+pseudowollastonite (CaSiO₃)+hemeskolaite_ss(Cr,Fe⁺³O₃). Pure andradite decomposes to pseudowollastonite (CaSiO₃)+hematite (Fe₂O₃) at 1,137±5 °C. Andradite thermal stability is increased by incorporation of Ca₃Cr₂Si₃O₁₂ component by 248 °C.At 1,264±5 °C pseudowollastonite+hematite react to liquid defining a thermal minimum of the CaSiO₃-Cr₂O₃-Fe₂O₃ ternary system. This minimum is located at about 64.5 wt.-% CaSiO₃, 0.5 wt.-% Cr₂O₃, and 35.0 wt.-% Fe₂O₃. Uvarovite and andradite bulk compositions start to melt at 1,420 °C and 1,265 ±5 °C, respectively.The unit-cell parameter for uvarovite is 11.999 (2) Å, the refractive index 1.866 (2). The substitution of Cr⁺³ by Fe⁺³ increases a and n almost linearly toward the andradite end member which displays a unit-cell parameter of 12.059 (3) Å and a refractive index of 1.887 (2).  相似文献   

Pure elastic stiffness of sand represented by response envelopes derived from cyclic triaxial tests with local strain measurements     

Knittel  Lukas  Wichtmann  Torsten  Niemunis  Andrzej  Huber  Gerhard  Espino  Edgar  Triantafyllidis  Theodoros 《Acta Geotechnica》2020,15(8):2075-2088

Acta Geotechnica - The elastic stiffness of a fine sand at small to moderate strains ( $$\varepsilon \le 2 \times 10^{-4}$$ ) has been studied based on cyclic triaxial tests on cube-shaped samples...  相似文献   

Uvarovite: Stability of uvarovite-grossularite solid solution at low pressure     

H. G. Huckenholz  D. Knittel 《Contributions to Mineralogy and Petrology》1975,49(3):211-232

Uvarovite (Ca₃Cr₂Si₃O₁₂) forms a complete solid solution series with grossularite (Ca₃Al₂Si₃O₁₂) below 855 ± 5 ° C at a total pressure of 1 atm. Pure uvarovite decomposes to pwo (CaSiO₃) + esk (Cr₂O₃) at 1385 ± 10 ° C. The incorporation of about 5 wt-% of Ca₃Al₂ Si₃O₁₂ component in the uvarovite structure raises the thermal stability of the garnet_ss to 1410 ± 5 ° C, and uvarovite₉₅ grossularite₀₅ melts incongruently to pwo (CaSiO₃) + coresk_ss ((Al, Cr)₂O₃) + L. Pure grossularite decomposes to wo (CaSi0₃) + geh (Ca₂Al₂SiO₇) + and (CaAl₂Si₂O₈) at 855 ± 5 ° C, grossularite thermal stability is increased by incorporation of Ca₃Cr₂Si₃O₁₂ component by 530 ° C. At 1280±5 ° C coresk_ss + L react to gar_ss + geh + an defining an invariant tequilibrium of the CaO-Cr₂O₃-Al₂O₃-SiO₂ quaternary system. Liquid reacts to gar_ss + pwo + geh + an at 1263 ±5 ° C terminating univariant and divariant liquid relations occurring along the join Ca₃Cr₂Si₃O₁₂-Ca₃Al₂Si₃O₁₂. The unit-cell parameter for uvarovite is 11.996(2) Å, the refractive index 1.865(3). The substitution of Cr by Al decreases a and n almost linearly toward the grossularite end member which displays a unit-cell parameter of 11.848(2) Å and a refractive index of 1.732 (1).  相似文献   

83 Ma rhyolite from Mindoro – evidence for Late Yanshanian magmatism in the Palawan Continental Terrane (Philippines)     

Ulrich Knittel 《Island Arc》2011,20(1):138-146

The discovery of a low‐grade meta‐rhyolite with an age of 83 ± 1 Ma documents a so‐far unknown episode of magmatism in northern Mindoro Island, which is located at the northeastern edge of the Palawan Continental Terrane. This terrane is thought to have rifted from Southeast China in the Oligocene as a result of the opening of the South China Sea. Rhyolite volcanism was widespread in southeastern China in the Cretaceous; hence this discovery provides the first direct link between the geological evolution of the Palawan Continental Terrane and Southeast China in Cretaceous time. In addition, it provides further evidence that the northeastern part of Mindoro is indeed part of the Palawan Continental Terrane and not part of the Philippine Mobile Belt to the east, a previously contentious issue.  相似文献   

Composition and Association of Arsenian Goldfieldite from the Marian gold deposit,Northern Luzon,Philippines     

Dr. U. Knittel 《Mineralogy and Petrology》1989,40(2):145-154

Summary Arsenian goldfieldite from the Marian Gold Mine, Philippines, which is hosted by the Cordon Syenite Complex, forms a solid solution series with Zn-rich tennantite, in contrast to goldfieldite from Goldfield (Nevada), Kamchatka and Uzbekistan, which are Zn-poor and form solid solution series with tetrahedrite. Goldfieldite from Butte (Montana) and the Lower Caucasus is very similar to the Marian goldfieldite. In all deposits except those at Butte and in the Lesser Caucasus, goldfieldite is associated with native Au, altaite, and Au-Ag-tellurides. Both the Marian gold deposit and the vein systems at Butte are associated with porphyry copper mineralization.

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Zusammensetzung und Paragenese von arsenhaltigem Goldfieldit aus der Goldlagstätte Marian, Nord-Luzon, Philippinen

Zusammenfassung As-reicher Goldfieldit der Marian Gold Lagerstätte (Philippinen) bildet eine Mischkristall-Reihe mit Zn-reichem Tennantit und steht damit in Gegensatz zu Goldfieldit von Goldfield (Nevada), Kamtschatka und Uzbekistan, welche Zn-arm sind und Mischkristalle mit Tetrahedrit bilden. Goldfieldit von Butte (Montana) und aus dem Kleinen Kaukasus hat eine ähnliche Zusammensetzung wie der der Marian Vererzung. Goldfieldit ist in allen Vorkommen, ausgenommen Butte und dem Kleinen Kaukasus, mit gediegen Au, Altait und Au-Ag-Telluriden vergesellschaftet. Sowohl die Marian Vererzung als auch die vererzten Gänge von Butte sind an porphyry copper Vererzungen gebunden.

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Diverse protolith ages for the Mindoro and Romblon Metamorphics (Philippines): Evidence from single zircon U–Pb dating          下载免费PDF全文

Ulrich Knittel  Monika Walia  Shigeyuki Suzuki  Carla B. Dimalanta  Graciano P. Yumul Jr. 《Island Arc》2017,26(1)

Within the north‐eastern part of the Palawan Continental Terrane, which forms the south‐western part of the Philippine archipelago, several metamorphic complexes are exposed that are considered to be rifted parts of the Asian margin in South‐East China. The protolith age(s) and correlations of these complexes are contentious. The largest metamorphic complex of the Palawan Continental Terrane comprises the Mindoro Metamorphics. The north‐eastern part of this metamorphic complex has recently been found to be composed of protoliths of Late Carboniferous to Late Permian protolith age. However, meta‐sediments exposed at the westernmost tip and close to the southern boundary of the exposure of the Mindoro Metamorphics contain detrital zircons and with U–Pb ages, determined by LA–ICP–MS, in the range 22–56 Ma. In addition, zircons as young as 112 Ma were found in a sample of the Romblon Metamorphics in Tablas. As the youngest detrital zircons provide an upper age limit for the time of deposition in meta‐sediments, these results suggest that the Mindoro and Romblon Metamorphics comprise protoliths of variable age: Late Carboniferous to Late Permian in NE Mindoro; Eocene or later in NW Mindoro; Miocene at the southern margin of the Mindoro metamorphics; and Cretaceous or later on Tablas. The presence of non‐metamorphic sediments of Late Eocene to Early Oligocene age in Mindoro (Lasala Formation), which are older than the youngest metasediments, suggests that metamorphism of the young meta‐sediments of Mindoro is the result of the collision of the Palawan Continental terrane with the Philippine Mobile Belt in Late Miocene. Similarities of the age spectra of zircons from the Eocene to Miocene metamorphics with the Eocene to Early Miocene Lasala Formation suggest that the protoliths of the young metamorphics may be equivalents of the Lasala Formation or were recycled from the Lasala Formation.  相似文献