Igneous Rock Associations 26. Lamproites, Exotic Potassic Alkaline Rocks: A Review of their Nomenclature, Characterization and Origins

Lamproite is a rare ultrapotassic alkaline rock of petrological importance as it is considered to be derived from metasomatized lithospheric mantle, and of economic significance, being the host of major diamond deposits. A review of the nomenclature of lamproite results in the recommendation that members of the lamproite petrological clan be named using mineralogical-genetic classifications to distinguish them from other genetically unrelated potassic alkaline rocks, kimberlite, and diverse lamprophyres. The names “Group 2 kimberlite” and “orangeite” must be abandoned as these rock types are varieties of bona fide lamproite restricted to the Kaapvaal Craton. Lamproites exhibit extreme diversity in their mineralogy which ranges from olivine phlogopite lamproite, through phlogopite leucite lamproite and potassic titanian richterite-diopside lamproite, to leucite sanidine lamproite. Diamondiferous olivine lamproites are hybrid rocks extensively contaminated by mantle-derived xenocrystic olivine. Currently, lamproites are divided into cratonic (e.g. Leucite Hills, USA; Baifen, China) and orogenic (Mediterranean) varieties (e.g. Murcia-Almeria, Spain; Afyon, Turkey; Xungba, Tibet). Each cratonic and orogenic lamproite province differs significantly in tectonic setting and Sr–Nd–Pb–Hf isotopic compositions. Isotopic compositions indicate derivation from enriched mantle sources, having long-term low Sm/Nd and high Rb/Sr ratios, relative to bulk earth and depleted asthenospheric mantle. All lamproites are considered, on the basis of their geochemistry, to be derived from ancient mineralogically complex K–Ti–Ba–REE-rich veins, or metasomes, in the lithospheric mantle with, or without, subsequent contributions from recent asthenospheric or subducted components at the time of genesis. Lamproite primary magmas are considered to be relatively silica-rich (~50–60 wt.% SiO2), MgO-poor (3–12 wt.%), and ultrapotassic (~8–12 wt.% K2O) as exemplified by hyalo-phlogopite lamproites from the Leucite Hills (Wyoming) or Smoky Butte (Montana). Brief descriptions are given of the most important phreatomagmatic diamondiferous lamproite vents. The tectonic processes which lead to partial melting of metasomes, and/or initiation of magmatism, are described for examples of cratonic and orogenic lamproites. As each lamproite province differs with respect to its mineralogy, geochemical evolution, and tectonic setting there is no simple or common petrogenetic model for their genesis. Each province must be considered as the unique expression of the times and vagaries of ancient mantle metasomatism, coupled with diverse and complex partial melting processes, together with mixing of younger asthenospheric and lithospheric material, and, in the case of many orogenic lamproites, with Paleogene to Recent subducted material.La lamproïte est une roche alcaline ultrapotassique rare d'importance pétrologique car elle est considérée comme dérivée du manteau lithosphérique métasomatisé, et d'importance économique, étant l'hôte de gisements de diamants majeurs. Un examen de la nomenclature des lamproïtes conduit à la recommandation que les membres du clan pétrologique des lamproïtes soient nommés en utilisant des classifications minéralogiques génétiques pour les distinguer des autres roches alcalines potassiques génétiquement non liées, de la kimberlite et de divers lamprophyres. Les noms « kimberlite du groupe 2 » et « orangéite » doivent être abandonnés car ces types de roches sont des variétés de véritables lamproïtes restreintes au craton de Kaapvaal. Les lamproïtes présentent une extrême diversité dans leur minéralogie qui va de la lamproïte à phlogopite et olivine, à la lamproïte à leucite et phlogopite et de la lamproïte à richtérite-diopside potassique titanifère, à la lamproïte à sanidine et leucite. Les lamproïtes à olivine diamantifères sont des roches hybrides largement contaminées par l'olivine xénocristique dérivée du manteau. Actuellement, les lamproïtes sont divisées en variétés cratoniques (par exemple Leucite Hills, États-Unis; Baifen, Chine) et orogéniques (méditerranéennes) (par exemple Murcie-Almeria, Espagne; Afyon, Turquie; Xungba, Tibet). Chaque province de lamproïte cratonique et orogénique diffère significativement par le contexte tectonique et les compositions isotopiques en Sr, Nd, Pb et Hf. Les compositions isotopiques indiquent que leur source est un manteau enrichi, ayant à long terme des rapports Sm/Nd bas et Rb/Sr élevés, par rapport à la Terre globale et au manteau asthénosphérique appauvri. Toutes les lamproïtes sont considérées, sur la base de leur géochimie, comme étant dérivées d'anciennes veines minéralogiquement complexes riches en K, Ti, Ba et ETR, ou métasomes, dans le manteau lithosphérique avec ou sans contributions ultérieures de composants asthénosphériques ou subductés récents au moment de la genèse. Les magmas primaires de lamproïte sont considérés comme relativement riches en silice (~ 50–60% en poids de SiO2), pauvres en MgO (3–12% en poids) et ultrapotassiques (~ 8–12% en poids de K2O) comme le montrent les lamproïtes hyalo à phlogopite de Leucite Hills (Wyoming) ou de Smoky Butte (Montana). De brèves descriptions sont données des cheminées de lamproïtes diamantifères phréatomagmatiques les plus importantes. Les processus tectoniques qui conduisent à la fusion partielle des métasomes et / ou à l'initiation du magmatisme sont décrits comme des exemples de lamproïtes cratoniques et orogéniques. Comme chaque province de lamproïte diffère en ce qui concerne sa minéralogie, son évolution géochimique et son cadre tectonique, il n'y a pas de modèle pétrogénétique simple ou commun pour leur genèse. Chaque province doit être considérée comme l'expression unique de l'époque et des caprices du métasomatisme du manteau ancien, associée à des processus de fusion partielle divers et complexes, ainsi qu'à un mélange de matériaux asthénosphériques et lithosphériques plus jeunes et, dans le cas de nombreuses lamproïtes orogéniques, à du matériel paléogène à récent subducté.

Development of Handling Qualities Criteria for Rotorcraft with Externally Slung Loads

Piloted simulations were performed on the NASA-Ames Vertical Motion Simulator (VMS) to explore handling qualities issues for large cargo helicopters, particularly focusing on external slung load operations. The purpose of this work was based upon the need to include handling qualities criteria for cargo helicopters in an upgrade to the U.S. Army's rotorcraft handling qualities specification, Aeronautical Design Standard-33 (ADS-33E-PRF). From the VMS results, handling qualities criteria were developed fro cargo helicopters carrying external slung loads in the degraded visual environment (DVE). If satisfied, these criteria provide assurance that the handling quality rating (HQR) will be 4 or better for operations in the DVE, and with a load mass ratio of 0.33 or less. For lighter loads, flying qualities were found to be less dependent on the load geometry and therefore the significance of the criteria is less. For heavier loads, meeting the criteria ensures the best possible handling qualities, albeit Level 2 for load mass ratios greater than 0.33

Reconstruction of magma chamber processes preserved in olivine-phlogopite micro-ijolites from the Oldoinyo Lengai, Tanzania

A detailed petrographic and mineralogical investigation of olivine-phlogopite micro-ijolite xenoliths from Oldoinyo Lengai, Tanzania indicates a complex evolutional history. These xenoliths consist of diverse textural subdomains characterized by minerals ranging from early-formed olivine, through diopside-hosted perovskite and phlogopite, to evolved aegirine-augite and titanite. Thermometry and mineral compositions in the subdomains suggest crystallization temperatures from 1070–970 °C to 850–700 °C at plutonic pressures and SiO2-activities controlled by perovskite-titanite equilibria. Double coronas are a characteristic textural feature of the olivine-phlogopite micro-ijolite, consisting of olivine cores surrounded by an inner clinopyroxene corona and an outer phlogopite corona. These double coronas might have formed during early magma chamber processes, including magma movement to a subsequent chamber resulting in dissolution of olivine with subsequent crystallization and accumulation of diopside and phlogopite. Diopside−aegirine-augite compositional zonation indicates several magma injections followed by cooling periods, during the formation of micro-ijolite groundmass. Mg# (80–83) and Ca (0.1–0.3 in wt%) contents of olivine together with the presence of primary melt inclusions in clinopyroxene, phlogopite, and nepheline indicate a magmatic origin from a possible parental olivine-nephelinite melt. There is evidence for subsolidus, or near-solidus, re-equilibration processes as indicated by the reaction of olivine with titanite forming symplectitic textures of ilmenite and diopside with minor zirconolite. Ti-exchange between phlogopite phenocrysts and other Ti-bearing minerals (perovskite, titanite, magnetite) resulted in ∼750 °C equilibrium temperatures for phlogopite, which are much lower than mafic magmatic (>900 °C) conditions. Calculated subsolidus temperatures suggest crystallization of olivine-phlogopite micro-ijolites over a 10–20 km depth interval

Neutral Hydrogen Associated with NGC 7129

Observations of the environment of the star-forming region NGC 7129 obtained with an angular resolution of 1' in the 21 cm line of H I are described. Two features of the image are extensively discussed: (1) a ring of H I emission about 30' in extent and (2) a relatively dense concentration of H I with unusually wide line profiles positionally coincident with the B star BD +65°1638. The H I ring is consistent with photodissociation of H2 by the interstellar UV radiation field at the surface of an extended molecular cloud in which both BD +65°1638 and NGC 7129 are situated. We further show that BD +65°1638 appears to be an unusual example of a "dissociating star" surrounded by an extensive region of photodissociated H2 and accompanied by a small H II region. The derived spectral type (B2.5) and the absolute magnitude for BD +65°1638 further suggest that the latter is very close to the birthline. The very young stellar age implied by the parameters of the H I region, considerably less than 104 yr, is discussed, and the properties of the H I region are compared with those of the prototype for this rare class of objects. We discuss both aspects within the context of star formation in NGC 7129

Vascular smooth muscle cell apoptosis in aneurysmal, occlusive, and normal human aortas

AbstractPurpose: Apoptosis is a physiologic mechanism of cell death that regulates mass and architecture in many tissues. Apoptosis has been described as a feature in human vascular atherosclerosis and large vessel structural integrity. We examined the extent of vascular smooth muscle cell (VSMC) apoptosis in aneurysmal, occlusive, and normal human aortic tissue. Methods: Tissue samples of aneurysmal, occlusive, and normal human infrarenal aorta were evaluated. DNA fragmentation detection methods, immunohistochemistry, and DNA electrophoresis determined VSMC density, VSMC apoptosis, and apoptosis markers. Apoptotic cells and VSMC nuclei were counted with the use of computer-generated image analysis. Aortic subtypes were compared statistically by analysis of variance. Results: Seventeen aneurysmal, ten occlusive, and five normal human aortas were evaluated. By α1-actin immunostaining, VSMC density was least in aneurysmal aortas (271.8 ± 13.5 cells/high-power field [HPF]) compared with occlusive aorta (278.2 ± 39.4 cells/HPF) and normal aortas (291.0 ± 25.4 cells/HPF; P = not significant). Presence of apoptotic VSMCs was demonstrated by terminal deoxynucleotidyl transferase fragment end labeling and propidium iodide nuclear staining. VSMC apoptosis was greatest within aneurysmal aortas with 11.7 ± 1.5 cells/HPF compared with occlusive aortas with 3.3 ± 0.8 cells/HPF (P <.05) and normal aortas with 3.75 ± 4.6 cells/HPF (P <.05). Significant differences in apoptosis markers, p53 or bcl-2, could not be demonstrated by immunohistochemistry or DNA electrophoresis in aortic subtypes. Conclusion: Apoptosis of VSMCs is increased and VSMC density is decreased within the medial layer of aneurysmal aortic tissue. Structural degeneration of aortic tissue at the cellular level contributes to aneurysmal formation. (J Vasc Surg 2000;31:567-576.

Prospectus, March 20, 1985

https://spark.parkland.edu/prospectus_1985/1007/thumbnail.jp

Solution Geochemistry of the Water of Limestone Terrains

Limestone groundwater flows mainly in openings it has solutionally enlarged, thus an understanding of the water\u27s state of saturation relative to calcite (the principal mineral component of limestone) is fundamental to an understanding of the nature and evolution of the limestone aquifer. This study investigated the Mammoth Cave-Sinkhole Plain (MCSP) and Cave Hollow (CH) aquifers in Kentucky, both in Missippian limestones. Both aquifers were always undersaturated with calcite. Except for completely ventilated vadose flows (usually) and some vadose seepage (occasionally), all recharges sampled (sinking streams, vadose flows, and vadose seepage) were also undersaturated. The lack of saturation in the MCSP aquifer was due to the introduction of carbon dioxide into the water in amounts difficult to explain by the carbon dioxide content of the above recharges. In both vadose flows and seepage, undersaturatlon tended to correlate directly with flow volume, and there was an inverse correlation between the amount of carbon dioxide and calcite saturation in most of the waters sampled. In vadose seepage this relationship was so strong as to suggest seasonal invariance of carbon dioxide content of the water prior to out gassing. Results suggest solutional enlargement is greatest near recharge points in ventilated aquifers (CH) but the carbon dioxide introduction phenomenon (MCSP) allows solution over wide areas in unventilated aquifers

Randomized Controlled Trial of Mechanical Thrombectomy Versus Catheter-directed Thrombolysis for Acute Hemodynamically Stable Pulmonary Embolism: Rationale and Design of the PEERLESS Study.

BACKGROUND The identification of hemodynamically stable pulmonary embolism (PE) patients who may benefit from advanced treatment beyond anticoagulation is unclear. However, when intervention is deemed necessary by the PE patient's care team, data to select the most advantageous interventional treatment option are lacking. Limiting factors include major bleeding risks with systemic and locally delivered thrombolytics and the overall lack of randomized controlled trial (RCT) data for interventional treatment strategies. Considering the expansion of the Pulmonary Embolism Response Team (PERT) model, corresponding rise in interventional treatment, and number of thrombolytic and non-thrombolytic catheter-directed devices coming to market, robust evidence is needed to identify the safest and most effective interventional option for patients. METHODS The PEERLESS study (ClinicalTrials.gov identifier: NCT05111613) is a currently enrolling multinational RCT comparing large-bore mechanical thrombectomy (MT) with the FlowTriever System (Inari Medical, Irvine, CA) vs catheter-directed thrombolysis (CDT). A total of 550 hemodynamically stable PE patients with right ventricular (RV) dysfunction and additional clinical risk factors will undergo 1:1 randomization. Up to 150 additional patients with absolute thrombolytic contraindications may be enrolled into a non-randomized MT cohort for separate analysis. The primary endpoint will be assessed at hospital discharge or 7 days post procedure, whichever is sooner, and is a composite of the following clinical outcomes constructed as a hierarchal win ratio: 1) all-cause mortality, 2) intracranial hemorrhage, 3) major bleeding, 4) clinical deterioration and/or escalation to bailout, and 5) intensive care unit admission and length of stay. The first 4 components of the win ratio will be adjudicated by a Clinical Events Committee, and all components will be assessed individually as secondary endpoints. Other key secondary endpoints include all-cause mortality and readmission within 30 days of procedure and device- and drug-related serious adverse events through the 30-day visit. IMPLICATIONS PEERLESS is the first RCT to compare two different interventional treatment strategies for hemodynamically stable PE and results will inform strategy selection after the physician or PERT determines advanced therapy is warranted