Investigation of flow fields within large scale hypersonic inlet models

Analytical and experimental investigations were conducted to determine the internal flow characteristics in model passages representative of hypersonic inlets for use at Mach numbers to about 12. The passages were large enough to permit measurements to be made in both the core flow and boundary layers. The analytical techniques for designing the internal contours and predicting the internal flow-field development accounted for coupling between the boundary layers and inviscid flow fields by means of a displacement-thickness correction. Three large-scale inlet models, each having a different internal compression ratio, were designed to provide high internal performance with an approximately uniform static-pressure distribution at the throat station. The models were tested in the Ames 3.5-Foot Hypersonic Wind Tunnel at a nominal free-stream Mach number of 7.4 and a unit free-stream Reynolds number of 8.86 X one million per meter

Geochronological and thermometric evidence of unusually hot fluids in an Alpine fissure of Lauzière granite (Belledonne, Western Alps)

A multi-method investigation into Lauzière granite, located in the external Belledonne massif of the French Alps, reveals unusually hot hydrothermal conditions in vertical open fractures (Alpine-type clefts). The host-rock granite shows sub-vertical mylonitic microstructures and partial retrogression at temperatures of &lt;&thinsp;400&thinsp;∘C during Alpine tectonometamorphism. Novel zircon fission-track (ZFT) data in the granite give ages at 16.3&thinsp;±&thinsp;1.9 and 14.3&thinsp;±&thinsp;1.6&thinsp;Ma, confirming that Alpine metamorphism was high enough to reset the pre-Alpine cooling ages and that the Lauzière granite had already cooled below 240–280&thinsp;∘C and was exhumed to &lt;&thinsp;10&thinsp;km at that time. Novel microthermometric data and chemical compositions of fluid inclusions obtained on millimetric monazite and on quartz crystals from the same cleft indicate early precipitation of monazite from a hot fluid at T&thinsp;&gt;&thinsp;410&thinsp;∘C, followed by a main stage of quartz growth at 300–320&thinsp;∘C and 1.5–2.2&thinsp;kbar. Previous Th-Pb dating of cleft monazite at 12.4&thinsp;±&thinsp;0.1&thinsp;Ma clearly indicates that this hot fluid infiltration took place significantly later than the peak of the Alpine metamorphism. Advective heating due to the hot fluid flow caused resetting of fission tracks in zircon in the cleft hanging wall, with a ZFT age at 10.3&thinsp;±&thinsp;1.0&thinsp;Ma. The results attest to the highly dynamic fluid pathways, allowing the circulation of deep mid-crustal fluids, 150–250&thinsp;∘C hotter than the host rock, which affect the thermal regime only at the wall rock of the Alpine-type cleft. Such advective heating may impact the ZFT data and represent a pitfall for exhumation rate reconstructions in areas affected by hydrothermal fluid flow.</p

A retrograde monazite-forming reaction in bearthide-bearing high-pressure rocks

Bearthite,Ca2Al[PO4](2)(OH),an aluminium phosphate that may contain up to similar to 10 wt% of light rare-earth elements (LREE) + Th, shows various breakdown textures in high-pressure metamorphic rocks. Two such reactions are described: (1) a pyrope-bearing kyanite-phengite-quartz (coesite) schist from the high-pressure Dora-Maira terrane, Italy, in which bearthite displays a symplectitic rim that consists of apatite + monazite; (2) a garnet-bearing muscovite-biotite gneiss of the Monte Rosa nappe, Italy, in which a symplectitic pseudomorph consisting of apatite + corundum + monazite occurs as an inclusion in allanite. In rocks with a high Al/Ca ratio, we suggest that bearthite is more stable than monazite as the LREE-bearing phase under high P/low T conditions (that is, a subduction zone environment). It breaks down to an assemblage of symplectitic monazite + apatite + corundum (or Al-silicate with free SiO2) during decompression. Bearthite that coexists with HREE-dominated minerals like xenotime does not show increased HREE contents. Because of its considerable Th-content, bearthite could be used to constrain the time of high-pressure metamorphism

A retrograde monazite-forming reaction in bearthite-bearing high-pressure rocks

Bearthite,Ca2Al[PO4](2)(OH),an aluminium phosphate that may contain up to similar to 10 wt% of light rare-earth elements (LREE) + Th, shows various breakdown textures in high-pressure metamorphic rocks. Two such reactions are described: (1) a pyrope-bearing kyanite-phengite-quartz (coesite) schist from the high-pressure Dora-Maira terrane, Italy, in which bearthite displays a symplectitic rim that consists of apatite + monazite; (2) a garnet-bearing muscovite-biotite gneiss of the Monte Rosa nappe, Italy, in which a symplectitic pseudomorph consisting of apatite + corundum + monazite occurs as an inclusion in allanite. In rocks with a high Al/Ca ratio, we suggest that bearthite is more stable than monazite as the LREE-bearing phase under high P/low T conditions (that is, a subduction zone environment). It breaks down to an assemblage of symplectitic monazite + apatite + corundum (or Al-silicate with free SiO2) during decompression. Bearthite that coexists with HREE-dominated minerals like xenotime does not show increased HREE contents. Because of its considerable Th-content, bearthite could be used to constrain the time of high-pressure metamorphism

Jiddat al Harasis 422: a ureilite with an extremely high degree of shock melting

The Jiddat al Harasis (JaH) 422 ureilite was found in the Sultanate of Oman; it is classified as a ureilitic impact melt breccia. The meteorite consists of rounded polycrystalline olivine clasts (35%), pores (8%), and microcrystalline matrix (57%). Clasts and matrix have oxygen isotopic values and chemical compositions (major and trace elements) characteristic of the ureilite group. The matrix contains olivine (Fo83-90), low-Ca pyroxene (En84-92Wo0-5), augite (En71-56Wo20-31), graphite, diamond, Fe-metal, sulfides, chromite, and felsic glass. Pores are partly filled by secondary Fe-oxihydroxide and desert alteration products. Pores are surrounded by strongly reduced silicates. Clasts consist of fine-grained aggregates of polygonal olivine. These clasts have an approximately 250 μm wide reaction rim, in which olivine composition evolves progressively from the core composition (Fo79-81) to the matrix composition (Fo84–87). Veins crossing the clasts comprise pyroxene, Fe-oxihydroxide, C-phases, and chromite. Clasts contain Ca-, Al-, and Cr-rich glass along olivine grain boundaries (~83-87 and chromite. Along pores, high Mg# compositions of silicates indicate that in a late stage or after melt crystallization FeO became less available and fO2 conditions were controlled by C-CO + CO2

Jiddat al Harasis 556: A howardite impact melt breccia with an H chondrite component

A petrographic and geochemical study was undertaken to characterize Jiddat al Harasis (JaH) 556, a howardite find from the Sultanate of Oman. JaH 556 is a polymict impact melt breccia containing highly shocked clasts, including mosaicized olivine and recrystallized plagioclase, set in a finely recrystallized vesicular matrix (grain diameter 76-92) and clinopyroxene (En48-62Wo7-15) are associated with orthopyroxene and olivine clasts like in a howardite. JaH 556 oxygen isotope data indicate that it has an anomalous bulk-rock composition as howardite, resulting from a mixture between HED material and at least one second reservoir characterized by a higher Δ17O. The bulk meteorite has a composition consistent with howardites, but it is enriched in siderophile elements (Ni = 3940 and Co = 159 ppm) arguing for a chondritic material as second reservoir. This is independently confirmed by the occurrence of chondrule relics composed of olivine (Fo56-80), orthopyroxene (En79Wo2), and plagioclase (An61-66). Based on oxygen isotopic signature, siderophile composition, and chondrule core Mg number (Fo80 and En79Wo2), it is proposed that JaH 556 is a howardite containing approximately 20% H chondrite material. This percentage is high compared with that observed petrographically, likely because chondritic material dissolved in the impact melt. This conclusion is supported by the observed reaction of orthopyroxene to olivine, which is consistent with a re-equilibration in a Si-undersaturated melt. JaH 556's unique composition enlarges the spectrum of howardite-analogs to be expected on the surface of 4 Vesta. Our data demonstrate that oxygen isotopic anomalies can be produced by a mixture of indigenous and impactor materials and must be interpreted with extreme caution within the HED group

Age of cleft monazites in the eastern Tauern Window: constraints on crystallization conditions of hydrothermal monazite

Monazite-bearing Alpine clefts located in the Sonnblick region of the eastern Tauern Window, Austria, are oriented perpendicular to the foliation and lineation. Ion probe (SIMS) Th–Pb and U–Pb dating of four cleft monazites yields crystallization ages of different growth domains and aggregate regions ranging from 18.99 ± 0.51 to 15.00 ± 0.51 Ma. The crystallization ages obtained are overlapping or slightly younger than zircon fission track ages but older than zircon (U–Th)/He cooling ages from the same area. This constrains cleft monazite crystallization in this area to *300–200 °C. LA-ICP-MS data of dated hydrothermal monazites indicate that in graphite-bearing, reduced host lithologies, cleft monazite is poor in As and has higher La/Yb values and U concentrations, whereas in oxidised host rocks opposite trends are observed. Monazites show negative Eu anomalies and variable La/Yb values ranging from 520 to 6050. The positive correlation between Ca and Sr concentration indicates dissolution of plagioclase or carbonates as the source of these elements. The data show that early exhumation and cleft formation in the Tauern is related to metamorphic dome formation caused by the collision of the Adriatic with the European plate and that monazite crystallization in the clefts occurred later. Our data also demonstrate that hydrothermal monazite ages offer great potential in helping to constrain the chronology of exhumation in collisional orogens