Contributions to mineral chemistry of Hawaiian rocks

Small gabbroic dikes of high TiO₂ content transect massive hawaiite in the Kaena Quarry, Waianae Range, Oahu. One dike studied consists of two rock types: (a) border zone alkali gabbro of high titanomagnetite and titanaugite content and, (b) interior mugearite that contains iron-rich pyroxenes and K-feldspar. The dike probably formed as an in situ latestage segregation enriched in TiO₂, SiO₂, and alkalis.     

Major-element vapor fractionation on the lunar surface: An unusual lithic fragment from the Luna 20 fines

A 250-μm fragment in the Luna 20 fines has a very fine-grained “igneous” texture and has the composition (wt.%): SiO₂, 41.1; TiO₂, 0.35; Al₂O₃, 27.2; Cr₂O₃, 0.14; FeO, 4.2; MnO, 0.06; MgO, 8.5; CaO, 17.8; Na₂O, 0.05; and K₂O < 0.02. It contains ～ 65% plagioclase An_99–100, ～ 15% olivine Fo₉₀, ～ 2% Mg-Al spinel and the remainder an unusual interstitial phase with composition SiO₂, 34.8; TiO₂, 1.78; Al₂O₃, 18.3; Cr₂O₃, 0.04; FeO, 14.1; MnO, 0.22; MgO, 5.0; CaO, 24.1; Na₂O, 0.34; K₂O < 0.02. This fragment probably represents a portion of a normal highland rock (anorthositic norite) which was heated to a very high temperature by impact, lost volatiles including SiO₂, and then partially crystallized. The observed phases and their inferred crystallization sequence are consistent with experimental results in the system CaOMgOAl₂O₃SiO₂ (Schairer and Yoder, 1969), assuming the unusual phase to be a residual glass. This type of internal fractionation, leading to silica depletion in the residuum, is different from that normally observed in lunar rocks and is attributed to slightly lower bulk SiO₂ resulting from vapor fractionation due to impact (which also results in lower Na₂O and other volatiles). Because differentiation of the type shown by this fragment is rare in lunar materials, we infer that such major-element vapor fractionation is uncommon on the surface of the moon. The experimental CaOMgOAl₂O₃SiO₂ phase relations also have a bearing on the lunar model proposed by D.L. Anderson in 1973: his “refractory” original lunar composition would differentiate to produce silica deficient liquids, like the unusual phase in our fragment, rather than the normal lunar crustal rocks.     

Das „Randcenoman“ der Nördlichen Kalkalpen und seine Bedeutung für den Ablauf der ostalpinen Deckenüberschiebungen und ihrer Schubweiten

Zusammenfassung Das Randcenoman erstreckt sich über 220 km als ein der Cenoman-Serie zugehöriger Grenzbereich gegen die Flyschzone am Nordrand der Kalkalpen vom Chiemsee bis in das Große Walsertal.An einer Anzahl durchgehender Profile wurden stratigraphische und sedimentologische Untersuchungen durchgeführt.Nach Mikrofaunen konnten neue stratigraphische Belege für eine örtliche Sedimentationsfortsetzung ohne erkennbare Schichtunterbrechung vom Alb bis in das Cenoman gefunden werden. Hinweise auf unterturones Alter ergaben sich an zwei Stellen. Die alttertiären Tratenbachschichten sind tektonisch von Randcenoman und Flysch abgegrenzt.Trotz eines heterogenen Gesteinsaufbaus in vertikaler und horizontaler Ausdehnung mit einer differenzierten Wechsellagerung von Peliten, Psammiten und Psephiten zeigt die Cenoman-Serie petrographische Konstanz in Gefüge und Mineralzusammensetzung, besonders im Geröllspektrum und der Schwermineralassoziation (Chromit-SpinellPicotit).Die Gesteine des Randcenoman sind in einem einheitlichen Ablagerungsraum sedimentiert worden. Das gilt auch für ihre Anteile in der Arosa-Zone im Allgäu und im Bregenzer Wald.Faziesbeziehungen zur Flyschzone gibt es nicht.Auf das Ablagerungsmilieu deuten Flachwasserbildungen hin, die im flachen Randbereich der Geosynklinale während langdauernder Ruhigwasserfazies mit episodischen Unterbrechungen abgelagert wurden.Die petrographische Zusammensetzung der allothigenen Gerölle, ihr Rundungsgrad, ihre metamorphe Beanspruchung und ihr Erhaltungszustand lassen Analogieschlüsse mit Gesteinen vom Verrucano-Typ zu. Im Zusammenhang mit der Tonmineralführung der Pelite (Kaolinit) und der typischen Chromit-Spinell-Beteiligung kann auf ein breites Festland geschlossen werden. An der Detritusanlieferung sind neben dem mesozoischen kalkalpinen Untergrund und Gesteinen vom Verrucano-Typ Unterostalpin und Südpenninikum beteiligt. Damit sind die nördlichen Kalkalpen im Süden der Tauern beheimatet.Der Zeitraum der Überschiebung über das Penninikum liegt nicht vor Unterturon.Mittelkretazische Bewegungen werden in der Cenoman-Serie nur untergeordnet wirksam, wo sich Konglomerate und Geröllpsammite an der Wende Alb-Cenoman horizontieren lassen.

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The Randcenoman extends over a distance of 220 km as a boundary part of the Cenomanian Series along the alpine Flysch at the northern margin of the Limestone Alps from Chiem-See to the Grosses Walsertal.Series of continuous profiles have been investigated by stratigraphic and sedimentologic methods.By use of microfossils it could be proved that sedimentation lasted from Albian up to Cenomanian without visible interruption. At two different localities it was possible to find references to Turonian age.The Tratenbach layers of Tertiary age are separated tectonically from the Randcenoman and the Flysch.The rocks of Randcenoman show a very constant texture and association of minerals, especially in boulders and heavy minerals (chromite-spinel-picotite).These rocks must have been sedimented into an uniform trough. Same may be said concerning their contents within the Arosa-Zone in the Algovian region and in the Woods of Bregenz. There are no connections possible with facies of the Flysch series.Sediments of low water type show that these series have been deposed along the margin of the Alpine Geosyncline during long times of stagnant waters with episodical interruptions.The petrographic composition of the allothigenic boulders, their roundness, metamorphic stress and their state of conversation allows comparisons with rocks of the series of the Verrucano.The existance of a vast continent may be derived from the clay contents of the pelites (kaolinite) and the typical appearance of chromite-spinel minerals. The detritus has been delivered partly by the Lower Austroalpine unit and southern Penninicum, and by Mesozoic series of the Limestone Alps and rocks of Verrucano type.Concluding the origin of the Northern Limestone Alps has to be located south of the Tauern window.The movement of the Austroalpine nappes over the Penninicum cannot have happened before Lower Turonian age. The movements of Middle Cretaceous time are only of small efficiency on the series of Cenomanian where conglomerates and psammites containing boulders could be dated to be of Albanian-Cenomanian age.

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Résumé Le «Randcenomanien» s'étend sur 220 Km comme un ensemble-limite appartenant au Cénomanien, au contact de la zone du Flysch à la bordure Nord des Alpes calcaires, depuis le Lac de Chiem jusqu'à la «Grosse Walsertal»,L'auteur a effectué, le long d'un certain nombre de profils, des recherches stratigraphiques et sédimentologiques.A partir des microfaunes, on peut trouver de nouvelles preuves stratigraphiques en faveur d'une continuité de la sédimentation de l'Albien jusqu'au Cénomanien, sans aucune interruption reconnaissable. A deux endroits l'auteur a trouvé des indications concernant la présence du Turonien inférieur. Les couches du «Tratenbach» appartenant au Tertiaire inférieur sont séparées par voie tectonique du «Randcenomanien» et du Flysch.Malgré une constitution lithologique hétérogène, tant suivant la verticale que l'horizontale, avec des alternances bien marquées de pélites, psammites et pséphites, la série du Cénomanien montre une constance pétrographique quant à la texture et la composition minéralogique, spécialement dans la gamme des galets et l'association des minéraux lourds (Chromite-Spinelle-Picotite).Les roches du «Randcenomanien» ont été sédimentées dans un bassin uniforme; c'est aussi le cas dans la zone d'Arosa dans l'Allgäu et de la forêt de Bregenz.Il n'y a aucune connection avec les facies de la zone du Flysch.Quant au milieu de sédimentation, is est donné par les formations d'eaux profondes qui ont été déposées dans la région de bordure peu profonde du géosynclinal au cours de périodes de longue durée, en eau calme, avec seulement quelques interruptions épisodiques.La composition pétrographique des galets allothigènes, leur degré d'arrondi, leur degré de métamorphisme et leur état de conservation permettent de faire des analogies avec des roches du type Verrucano. Compte tenu aussi des minéraux argileux intervenant dans la constitution des pélites (kaolinite) et à la participation typique de la Chromite et du spinelle, on en arrive à la conclusion que le continent fournisseur de ces sédiments a été assez vaste. Aux apports détritiques du Mésozoïque inférieur des Alpes calcaires et des roches du type «Verrucano», sont venus s'ajouter ceux en provenance de l'Austroalpin inférieur et du Pennique méridional. C'est pourquoi le lieu d'origine des «Alpes calcaires» du Nord doit se trouver au sud des Tauern.Le chevauchement sur le Penninicum n'a pas eu lieu avant le Turonien inférieur.Les mouvements Crétacé inférieur dans le Cénomanien n'ont été que peu actifs, là où des conglomérats et des psammites à galets se sont épandus entre l'Albien et le Cénomanien.

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Randcenoman 220 , Chiem Große Valsertal. . . , . Tratenbach Randcenoman . , , , , , (- -). Randcenoman . Arosa Allgäu Bregenzer Wald. . . , , . , () - . , . . . Tauern. . , , / .

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Erweiterte Fassung eines am 25. Februar 1972 auf der 62. Jahrestagung der Geologischen Vereinigung in Frankfurt gehaltenen Vortrages.     

Oxide minerals in lithic fragments from Luna 20 fines

One hundred and seventy-six oxide mineral grains in the Luna 20 samples were analyzed by electron microprobe. Spinel is the most abundant oxide, occurring in troctolite fragments. Next most abundant is ilmenite, which occurs in all rock types except those containing spinel. Chromite also occurs in all rock types except those containing spinel. Minor amounts of ulvöspinel, armalcolite, zirkelite, baddeleyite and an unidentified TiO₂-rich phase were also found.Spinel grains are predominantly spinel-hercynite solid solutions, commonly with very minor chromite. The $\text{Fe}\text{(Fe + Mg)}$ ratio is generally lower than in spinel from Apollo 14 rocks. Chromites in non-mare rocks are similar to those from mare rocks. Ilmenite of mare origin is Mg-poor and Zr-rich compared to non-mare ilmenite; these elements may therefore be useful in determining the origin of ilmenite grains.Phase equilibria considerations suggest that spinel troctolite crystallized from a melt high in alumina; a likely candidate is the high-alumina basalt of Prinzet al. (1973a).Sub-micron wide rods of metallic Fe occur in plagioclase grains and may have formed by sub-solidus reduction processes.     

Mineralogy,petrology and chemistry of lithic fragments from Luna 20 fines: origin of the cumulate ANT suite and its relationship to high-alumina and mare basalts

Bulk analyses of 157 lithic fragments of igneous origin and analyses of their constituent minerals (plagioclase, pyroxene, olivine, Mg-Al spinel, chromite, ilmenite, armalcolite, baddeleyite, zirkelite, K-feldspar, interstitial glass high in SiO₂ and K₂O) have been used to characterize the lunar highland rock suites at the Luna 20 site. The predominant suite is composed of ANT (anorthositic-noritic-troctolitic) rocks, as found at previous Apollo and Luna sites. This suite consists of an early cumulate member, spinel troctolite, and later cumulate rocks which are gradational from anorthosite to noritic and troctolitic anorthosite to anorthositic norite and troctolite; anorthositic norite is the most abundant rock type and its composition is close to the average composition for the highland rocks at this site. Spinel troctolite is a distinctive member of this suite and is characterized by the presence of Mg-Al spinel, magnesian olivine (average, Fo₈₃), and plagioclase. High-alumina basalt with low alkali content is another important rock type and melt of this composition may be parental to the cumulate ANT suite. Alkalic high-alumina basalt (KREEP) was not found in our sample, but may be genetically related to the ANT suite in that it may have formed by partial melting of rocks similar to those of the ANT suite. Fractional crystallization of low alkali, high-alumina basalt probably cannot produce alkalic high-alumina basalt because the enrichment in KREEP component is many times greater than the simultaneous change in major element components. Formation of alkalic high-alumina basalt by mechanical mixing of ANT rocks with very KREEP-rich components is not likely because the high-alumina basalt suite falls on a cotectic in the anorthiteolivine-silica system. Mare basalts may also be genetically related in that they may have been derived by remelting of rocks formed from residual liquids of fractional crystallization of parental low-alkali, high-alumina basalt, plus mafic cumulate crystals; the resultant melt would have a negative Eu anomaly and high $\text{Fe}\text{Mg}$ and $\text{pyroxene}\text{plagioclase}$ ratios.     

On the stability of the solar wind

The stability of the solar wind is studied in the case of spherical symmetry and constant temperature. It is shown that the stability problem must be formulated as a mixed initial and boundary-value problem in which are prescribed the perturbation values of velocity and density at an initial time and additionally the velocity perturbation at the base of the corona for all times. The solution is constructed by linear superposition of normal solutions, which contain the time only in an exponential factor. The stability problem becomes a singular eigenvalue problem for the amplitudes of the velocity and pressure perturbations, since additionally to the boundary condition at the base of the corona one must add the condition that the amplitudes behave regularly at the critical point. It is proved that only stable eigenvalues exist.     

THE BEAVER-HARRISON,BEAVER COUNTY,UTAH L6 CHONDRITE

The Beaver-Harrison, Utah chondrite (find July 24, 1979), a single, shock-veined stone of 925 grams, consists of major olivine (Fa_25.0), low-Ca pyroxene (En_77.3Fs_21.1Wo_1.6) and metallic nickel-iron; minor troilite and plagioclase (Ab_82.6An_11.1Or_6.3), accessory high-Ca pyroxene (En_47.0Fs_8.5Wo_44.5), chromite (Cm_8.7Sp_10.6Uv_9.4Pc_0.6Hc_0.7), chlorapatite and whitlockite; and hydrous ferric oxide of terrestrial weathering origin. Mineral compositions indicate L-group classification, and homogeneity of minerals, highly recrystallized texture and presence of clear plagioclase suggest that the meteorite belongs to petrologic type 6.     

A Sr isotope study on fluorite and siderite from post-orogenic mineral veins in the eastern Harz Mountains,Germany

Rb–Sr isotope data for siderite and fluorite from sediment-hosted epithermal mineral veins in the eastern Harz Mountains (Germany) are presented. Several fluorite and siderite-bearing paragenetic stages have been proposed for these veins, with the most important mineralization being related to a quartz–sulfide and a subsequent calcite–fluorite–quartz stage, which occurred at 226±1 and 209±2 Ma, respectively. Our Rb–Sr data do not permit the identification of distinct generations of siderite and fluorite, but rather reveal straight internal mixing relations, reflecting mixing of fluids or differential fluid–rock interaction processes. This indicates merely two significant phases of mineral deposition related to the quartz–sulfide and calcite–fluorite–quartz stages. It is shown that the Paleozoic sedimentary host rocks of the veins are the most likely source for the siderite Sr, whereas fluorite displays a two-component mixture between sedimentary Sr and radiogenic Sr derived from locally occurring Permian metavolcanic rocks. Editorial handling: B. Lehmann