Petrology and chemistry of two “large” granite clasts from the moon

Pristine granite clasts in Apollo-14 breccias 14321 and 14303 have estimated masses of 1.8 and 0.17 g, respectively. The 14321 clast is ～ 60% K-feldspar and 40% quartz, with traces of extremely Mg-poor mafic silicates and ilmenite. The 14303 clast is roughly 33% plagioclase, 32% K-feldspar, 23% quartz, 11% pyroxene, and 1% ilmenite; pyroxene and ilmenite are moderately Mg-rich; plagioclase and pyroxene are strongly zoned. Both clasts are severely brecciated, but monomict (pristine). Both have abundant graphic intergrowths of K-feldspar with quartz. Unlike the majority of similar Earth rocks, both clasts are devoid of hydrous phases. The bulk composition of the 14321 clast is similar to those of several other lunar granitic samples, but the 14303 clast is unique: it bears as close a resemblance to KREEP as it does to other lunar granites. Silicate liquid immiscibility may explain why the granites are low in REE relative to KREEP.     

Solubility of corundum in supercritical water

Isothermal (670–700°C) solubility of corundum in supercritical water, within the stability range of corundum as a phase of the system Al₂O₃-H₂O, has been determined by the weight loss method. Experiments were performed in the pressure range 2.5 to 6 kbar in cold seal hydrothermal equipment at 670 ± 5°C using gold tubing. The overall uncertainty of the solubility values obtained was 8%. Experiments in the pressure range 10 to 20 kbar were performed in a piston cylinder apparatus at 700°C using sealed gold capsules held by supporting steel containers. The overall uncertainty of the solubility values obtained was estimated to be 10%.All data could be fitted by the linear equation S_[ppmAl2O3] = ?12.37 + 7.24 · p[_kbar] with correlation coefficient r = 0.9963. Separate fits of hydrothermal and piston cylinder results yielded a small difference between the two data sets, which is due rather to the experimental uncertainty than to the small temperature difference.     

The matrices of unequilibrated ordinary chondrites: Implications for the origin and history of chondrites

The matrices of sixteen unequilibrated ordinary chondrites (all witnessed falls) were studied microscopically in transmitted and reflected light and analyzed by electron microprobe. Selected specimens were also studied by scanning electron microscopy. These studies indicate that the fine-grained, opaque, silicate matrix of type 3 unequilibrated chondrites is compositionally, mineralogically and texturally distinct from the chondrules and chondrule fragments and may be the low temperature condensate proposed by Larimer and Anders (1967, 1970). Examination of the matrices of unequilibrated chondrites also shows that each meteorite has been metamorphosed, with the alteration ranging in intensity from quite mild, where the matrix has been only slightly altered, to a more severe metamorphism that has completely recrystallized the opaque matrix. Most of the metamorphic changes in the matrix occurred without significant effects on the compositions or textures of the chondrules. The metamorphic alteration probably resulted from a combination of processes including thermal metamorphism and the passage of shock waves. The present appearance of each unequilibrated chondrite is a result of the particular temperature and pressure conditions under which it and its components formed, plus the subsequent metamorphic alteration it experienced.     

Subsolidus orthopyroxene-clinopyroxene systematics in the system CaO-MgO-SiO2 to 60 kb: a re-evaluation of the regular solution model

On the basis of an increased set of experimental data, covering the miscibility gap between orthopyroxene and clinopyroxene from 2 to 60 kb with a temperature range of 850–1,500° C, we present a new version of a regular solution model. The model with two independent regular solutions for opx and cpx is capable of reproducing experimental data in the system CaO-MgO-SiO₂ over a large range of temperatures and pressures. It is qualitatively in agreement with observed stability regions for an Fe-free low-Ca pyroxene, termed pigeonite. The model is constrained by and thus consistent with calorimetric measurements on pyroxenes. The simple form of equations provides a good starting point for the development of more reliable thermometers based on the miscibility gap.Abbrevations Used in the Text cpx clinopyroxene - di diopside, CaMgSi₂O₆ - en enstatite, Mg₂Si₂O₆ - pig pigeonite - opx orthopyroxene - H (i) molar enthalpy difference (of reaction i) - S (i) molar entropy difference of reaction (i) - V (i) molar volume difference of reaction (i) - X[i]j mole fraction of i in phase j     

Zur Geologie des Thurntaler Quarzphyllits und des Altkristallins südlich des Tauernfensters (Ostalpen,Südtirol)

Zusammenfassung Geologische und petrographische Untersuchungen im Thurntaler Quarzphyllit und im angrenzenden Altkristallin südlich des Tauernfensters lassen einen mehrfachen Wechsel von Deformation und Kristallisation erkennen. Im gesamten Untersuchungsbereich waren vor allem Deformationen gefügeprägend für die Gesteine.Für den Thurntaler Quarzphyllit wird ein lithostratigraphisches Schema vorgestellt, welches ein altpaläozoisches Alter wahrscheinlich macht. Die tektonische Grenze zwischen Altkristallin und Quarzphyllit war mehrphasig aktiv. Sie bildet eine breite Mylonitzone und läuft spitzwinklig auf die Periadriatische Linie zu. Tektonische Daten zeigen gemeinsam mit petrographischen Befunden an, daß Altkristallin und Quarzphyllit die Diaphthorese und alle nachfolgenden gefügeprägenden Phasen bereits in enger Nachbarschaft zueinander erlebt haben. Für die absolute zeitliche Einstufung der einzelnen Deformationsund Kristallisationsphasen muß ein breiter Interpretationsspielraum verbleiben, da radiometrische Daten fehlen.Die Markinkele-Linie wird neben DAV, KV und Drautallinie als vierte wichtige tektonische Trennfuge im Altkristallin südlich des Tauernfensters eingeführt. Die mehrphasigen Deformationen an dieser Linie liefen in verschiedenen Tiefenlagen ab. Zuletzt sind oberflächennahe Kaltdeformationen festzustellen.Die Bedeutung der Periadriatischen Linie zu alpidischer Zeit muß im Zusammenhang mit den erwähnten intrakristallinen Störungen gesehen werden, da diese alle in die Periadriatische Linie einmünden.

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Geological and petrographical investigations in the Thurntaler Quarzphyllit and in the Altkristallin south of the Tauern Window show a polyphase change of deformation and crystallisation. The metamorphic textures of the whole investigated zone are mainly controlled by deformation phases.A lithostratigraphic column is presented for the Thurntaler Quarzphyllit which supports the Early Paleozoic age of this unit. The tectonic border between Altkristallin and Quarzphyllit was active for several times. A large zone of mylonites was formed which converges at a low angle with the Periadriatic Lineament. Tectonical data and petrographic studies show that Altkristallin and Quarzphyllit have undergone together a phase of retrograde metamorphism and all following stages of geological history. As radiometric data are lacking, a wide range of possibilities must be kept open in dating single deformation or crystallisation phases.Additional to the DAV, KV and Drautal-Line, the Markinkele-Line is established as a fourth important fault within the Altkristallin south of the Tauern Window. At this line, polyphase deformations took place at different crustal niveaus, at last ending up in mylonitisation near the surface.The significance of the Periadriatic Lineament at alpine times must be regarded in context with all above mentioned intracrystalline faults, as they all geometrically join the Periadriatic Lineament.

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Résumé Les recherches géologiques et pétrographiques dans la Quartzphyllite de la Thurntal et dans l'Altcristallin adjacent au Sud de la Fenêtre des Tauern font apparaître un changement répété de la déformation et de la cristallisation. Dans toute la région, ce sont surtout des déformations qui ont affecté la texture des roches.Pour la quartzphyllite de la Thurntal il est proposé un schéma lithostratigraphique qui rend vraisemblable un âge paléozoïque ancien. La limite tectonique entre l'Altcristallin et la quartzphyllite est passée par plusieurs phases d'activité. Elle forme une large zone mylonitisée et s'allonge avec un angle aigu avec la ligne périadriatique. Les données tectoniques comme les analyses pétrographiques, montrent que l'Altcristallin et la quartzphyllite ont subi ensemble une diaphtorèse et toutes les phases déformatives suivantes intervenues dans leur proximité immédiate. Etant donné l'absence de données radiométriques, une grande latitude d'interprétation doit être laissée pour la datation absolue de chacune des phases de déformation et de cristallisation.La ligne Markinkele est intégrée, à côté de DAV, KV et de la ligne de la Drautal, comme quatrième niveau tectonique séparatif important au Sud de la fenêtre des Tauern. Les déformations polyphasées le long de cette ligne se déroulent dans des niveaux de profondeur différents. Finalement on peut constater des mylonitisations à froid survenues près de la surface.La signification de la ligne périadriatique au cours de la période alpidique doit être vue en liaison avec les failles intracristallines mentionnées, parce qu'elles débouchent toutes dans la ligne périadriatique.

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Das Alter der Dolerolenus-Fauna

Zusammenfassung Neue Funde von Dolerolenidae aus Spanien und Marokko beweisen, daß dieDolerolenus-Fauna (Olenopsis-Fauna) älter ist als dieHolmia-Fauna von N-Europa. (Bisher hatte man dieOlenopsis-Fauna für hoch-unter-kambrisch oder gar noch jünger gehalten.) AuchBigotina gehört zu den Dolerolenidae. Demnach ist der Archaeocyathiden-Kalk der Normandie ein Äquivalent des unterkambrischen Kalk-Dolomit-Horizontes von S-Europa und SE-Deutschland.     

Contributions to the mineral chemistry of Hawaiian rocks

Detailed examination of rhyodacite from a new locality on Kauaopuu Ridge, Oahu, Hawaii (the second occurrence of rhyodacite in the Hawaiian volcanic province) yields the following results and conclusions: i) Bulk composition, mineral content, texture, and geographic location indicate that the newly found rhyodacite is part of the Mauna Kuwale rhyodacite flow described by Macdonald (1940); ii) Mineral phases include plagioclase (An_53–23), biotite, orthopyroxene, Ti-rich hornblende, titaniferous magnetite, and ilmenite; iii) Groundmass glass, about 75% by volume, is similar in bulk composition to oceanic rhyolite such as that of Easter Island and Iceland; iv) Similarity in composition between rhyodacite groundmass glass, described here, and bulk composition of oceanic rhyolite from Easter Island and Iceland, suggests that the latter could conceivably have formed by crystal fractionation of a rhyodacitic magma.     

Silurian-Devonian and Jurassic Thermal Events in the Ordos Basin, China: Indications from K-Ar Dating on Illites

In the Ordos basin, two distinct thermal events of different ages have been identified for the first time by means of K-Ar dating combined with illite crystallinity analysis. For the Late Triassic and Late Permian samples, the K-Ar ages of the < 0.2μm fractions (159-173 Ma) reflect an illitization age related to the Yanshanian movement and indicate a short thermal event in the Middle Jurassic; the K-Ar ages of the <2 μm fractions (210-308 Ma) are interpreted as mixed ages of detrital material and authigenic illites. The K-Ar ages of both < 0.2μm and < 2μm fractions of a Middle Cambrian sample (368 Ma and 419 Ma) correspond to the ages of the metamorphism and earliest granite intrusion in the northern Caledonian Qinling fold zone (380-420 Ma) and show a thermal event during Silurian-Devonian time.     

鄂尔多斯盆地志留—泥盆纪和侏罗纪热事件—伊利石K—Ar年龄证据

利用伊利石K-Ar测年法,结合伊利石结晶度分析,首次在鄂尔多斯盆地确定出两期不同时代热事件。晚三叠世和晚二叠世<0.2μm粒级的岩石样品的K-Ar年龄(159-173Ma)反映了与燕山运动有关的伊利石化年龄,指示有一期中侏罗世的热事件;其<2μm粒级的K-Ar年龄(210-308Ma)则被解释为碎屑物和自生伊利石的混合年龄。中寒武世<0.2μm和<2μm粒级的岩石样品K-Ar年龄(368Ma与419Ma)对应于北秦岭加里东褶皱带变质作用与最早期花岗岩侵入的时代(380-420Ma),表明在志留-泥盆纪发生了一期热事件。