The prestigious red Imperial Porphyry was quarried from Mons Porphyrites in the Red Sea Mountains of Egypt. It was reserved for imperial use in Rome and Constantinople and widely reused in Romanesque and Renaissance times. The mineralogy and petrology of the porphyry collected at Mons Porphyrites were treated in Part I of this report. The rocks were moderately altered; greenschist facies alteration took place under essentially isochemical conditions but relatively high oxygen fugacity. The rocks retain many magmatic textures.Whole-rock chemical analyses show that we deal with high-K to medium-K calc-alkaline andesites and dacites with a trace element spectrum typical of volcanic rocks from an Andean subduction-zone setting. Four rock samples yielded an errorchron with an age of 560 +/- 42 Ma and an initial Sr-87/Sr-86 ratio of 0.70283 +/- 0.00011. Using Nd isotope data, values of T-DM from 0.84 to 0.88 Ga and epsilon Nd from +5.1 to +5.7 were inferred. The magmas which led to formation of the Imperial Porphyry appear to be derived from a subduction-modified depleted mantle and underwent only minor contamination by older continental crust. Trace-element features, notably the high Th, U, K, Rb and Cs contents, are consistent with crust contamination. Imperial Porphyry erupted during the second Great Oxygenation Event of the Earth atmosphere.Mineralogical observations as well as rock colour and texture, particularly the pleochroic epidote - piemontite, should allow archaeologists to reliably assign pieces of Imperial Porphyry to their Egyptian source. Major- and trace-element rock analysis or electron microprobe mineral analysis will confirm the assignment.

The U–Th–REE deposit located at the Kvanefjeld plateau in the north-west corner of the Ilímaussaq alkaline complex, South Greenland, consists of lujavrites which are melanocratic agpaitic nepheline syenites. The fine-grained lujavrites of the Kvanefjeld plateau can be divided into a northern and a southern part with an intermediate zone between them. The northern part is situated along the north contact of the Ilímaussaq complex and continues east of the Kvanefjeld plateau as a lujavrite belt along the contact. This part has relatively ‘low’ contents of U, Th, and REE, and hyperagpaitic mineralogy is restricted to its highest-lying parts. The fine-grained lujavrites of the intermediate and southern part of the Kvanefjeld plateau occur between and below huge masses of country rocks which we show are practically in situ remnants of the roof of the lujavrite magma chamber. These lujavrites have high contents of U, Th, and REE, and hyperagpaitic varieties with naujakasite, steenstrupine and villiaumite are widespread. We present a model for the formation of the fine-grained lujavrites of the Kvanefjeld plateau. In this model, an off-shoot from the large lujavrite magma body in the central part of the complex intruded into a fracture zone along the north contact of the Ilímaussaq complex and was forcefully emplaced from north-west to south-east. The intruding lujavrite magma was bounded to the west, north, and at its roof by strong volcanic country rocks, and to the south by the weaker, earlier rocks of the complex. The magma stored in the fracture crystallized, squeezing volatile and residual ele-ments upwards. A subsequent violent explosion opened up fractures in the weaker southern rocks, and the residual volatile-enriched magma was squeezed into fractures in augite syenite, naujaite, and also in the overlying volcanic roof rocks. The removal of the volatile-rich lujavrite magma in the upper part of the fracture-bounded magma chamber made room for the rise of volatile-poor magma from the lower part of the magma chamber, and these lujavrites crystallized to form the northern continuous lujavrite belt. Transfer and accumulation of volatile and residual elements in a lujavrite magma crystallizing below an impervious cover played a key role in the formation of the Kvanefjeld U–Th–REE deposit, as it also did in the crystallization of the lujavrite magma body in the central part of the Ilímaussaq complex.

Microrhythmic layering is locally developed in agpaitic arfvedsonite lujavrite from the Ilímaussaq alkaline complex, South Greenland. Three–15-cm-thick laminated dark layers alternate with 1–10-cm-thick, light-coloured granular urtitic layers. Dark layers are uniform (isomodal) but the urtitic layers are enriched in early nepheline and eudialyte in their lower parts and in late analcime and REE phosphate minerals in the upper parts. The layers are separated by sharp contacts; they are draped around rafts from the overlying roof zone and lack structures indicative of current processes or post-cumulus deformation. Compared with the background arfvedsonite lujavrite of the complex, the dark layers are richer in sodalite, microcline and arfvedsonite and poorer in analcime and eudialyte. They have higher K2O, Cl, FeO⁎ and S but lower Na2O, H2O+, Zr and P contents, the opposite of the light-coloured layers. The complementary chemistry of the two types of layers oscillates about the composition of the background arfvedsonite lujavrite. Layers probably formed in a stagnant bottom layer of the lujavrite magma chamber. Each layer started as a liquid layer which exchanged components with the underlying crystallization front. On cooling, it crystallized primocrysts and exchanged components with the overlying magma which became a new, complementary liquid layer and, during further cooling and burial within the sequence of layers, it underwent largely closed-system interstitial crystallization. Exhaustion of Cl and a sharp decrease in aNaCl relative to aH2O terminated the crystallization of a sodalite-rich dark layer and initiated abundant crystallization of nepheline in the overlying liquid layer (urtitic layer). The layered sequence represents a local K2O-, Cl-rich but Na2O-, H2O-poor facies of arfvedsonite lujavrite and may have formed by exchanging components with sodalite-bearing rafts from the roof zone.

coronary artherosclerosis. J Mol Cell Cardiol 5: 515-526 Vary TC, Schaffer SW (1978) Role of adenine nucleotides in ischemic injury (abstr). Fed Proc 37: 230 Wiedmeier VT, Rubio R, Berne RM (1972) Incorporation and turnover of adenosine-U-'C in perfused guinea pig myocardium. Am J Physiol 223: 51-54 Williamson JR, Corkey BE (1969) Assays of intermediates of the citric acid cycle and related compounds by fluorometric enzyme methods. Methods Enzymol 13: 439-513 Williamson JR, Schaffer SW, Ford C, Safer B (1976) Contribution of tissue acidosis to ischemic injury in the perfused rat heart. Circulation 53 (suppl III): 1-14

We present the results of a regional study of oxygen and Sr-Nd-Pb isotopes of Pleistocene to Recent arc volcanism in the Kamchatka Peninsula and the Kuriles, with emphasis on the largest caldera-forming centers. The δ18O values of phenocrysts, in combination with numerical crystallization modeling (MELTS) and experimental fractionation factors, are used to derive best estimates of primary values for δ18O(magma). Magmatic δ18O values span 3.5‰ and are correlated with whole-rock Sr-Nd-Pb isotopes and major elements. Our data show that Kamchatka is a region of isotopic diversity with high-δ18O basaltic magmas (sampling mantle to lower crustal high-δ18O sources), and low-δ18O silicic volcanism (sampling low-δ18O upper crust). Among one hundred Holocene and Late Pleistocene eruptive units from 23 volcanic centers, one half represents low-δ18O magmas (+4 to 5‰). Most low-δ18O magmas are voluminous silicic ignimbrites related to large >10 km3 caldera-forming eruptions and subsequent intracaldera lavas and domes: Holocene multi-caldera Ksudach volcano, Karymsky and Kurile Lake-Iliinsky calderas, and Late Pleistocene Maly Semyachik, Akademy Nauk, and Uzon calderas. Low-δ18O magmas are not found among the less voluminous products of stratovolcano eruptions and these volcanoes do not show drastic changes in δ18O during their evolution. Additionally, high-δ18O(magma) of +6.0 to 7.5‰ are found among basalts and basaltic andesites of Bezymianny, Shiveluch, Avachinsky, and Koryaksky volcanoes, and dacites and rhyolites of Opala and Khangar volcanoes (7.1–8.0‰). Phenocrysts in volcanic rocks from the adjacent Kurile Islands (ignimbrites and lavas) define normal-δ18O magmas. The widespread and volumetric abundance of low-δ18O magmas in the large landmass of Kamchatka is possibly related to a combination of near-surface volcanic processes, the effects of the last glaciation on high-latitude meteoric waters, and extensive geyser and hydrothermal systems that are matched only by Iceland. Sr and Pb isotopic compositions of normal and low-δ18O, predominantly silicic, volcanic rocks show negative correlation with δ18O, similar to the trend in Iceland. This indicates that low-δ18O volcanic rocks are largely produced by remelting of older, more radiogenic, hydrothermally altered crust that suffered δ18O-depletion during >2 My-long Pleistocene glaciation. The regionally-distributed high-δ18O values for basic volcanism (ca. + 6 to +7.5‰) in Kamchatka cannot be solely explained by high-δ18O slab fluid or melt (± sediment) addition in the mantle, or local subduction of hydrated OIB-type crust of the Hawaii-Emperor chain. Overall, Nd-Pb isotope systematics are MORB-like. Voluminous basic volcanism (in the Central Kamchatka Depression in particular) requires regional, though perhaps patchy, remobilization of thick (30–45 km) Mesozoic-Miocene arc roots, possibly resulting from interaction with hot (ca. 1300°C), wedge-derived normal-δ18O, low-87Sr/86Sr basalts and from dehydration melting of lower crustal metabasalts, variably high in δ18O and 87Sr/86Sr.

The Ilímaussaq alkaline complex is one of the latest members of the Mesoproterozoic Gardar igneous province. It was emplaced in three phases, (1) augite syenite, (2) alkali acid rocks and (3) the dominant agpaitic nepheline syenites. The immediate parent for the nepheline syenites is the augite syenite whose geochemical features, such as the low Zr/Nb ratio (3.7), match benmoreites from a nearby alkali basalt series. The agpaitic nepheline syenites are characterised by exceptionally high contents of Zr, Hf, Nb, Ta, REE, Th, U, Sn, Li, Be, Rb, Zn, Pb, Sb, W, Mo, As and Ga, and the volatile elements F, Cl, Br, I and S but exceptionally low levels of Ba, Sr, Co, Cu, Ni, Sc, V and Cr. Fractionation of cumulus phases with a distinctive geochemistry, such as sodalite (rich in Cl, Br, I, B), eudialyte (Zr, Hf, Nb, Ta, W, As) and arfvedsonite (Co, Sc, V, Cr), caused exhaustion of these elements in the residual magmas. The agpaitic magmas underwent extreme fractionation with the final lujavrite forming after 99% crystallisation of the augite syenite. Zirconium was apparently soluble in Ilímaussaq melts up to a concentration of c. 9000 ppm. Whole-rock analyses define a number of discrete Zr–U arrays which are restricted to certain intervals of the cumulate stratigraphy and are taken as evidence for liquid layering in the Ilímaussaq magma chamber. The distribution of the less common trace elements (Bi, Cd, Co, Ge, In, I, Hg, Sc, Se, V, W) and of the more abundant trace elements which failed to form minerals (Br, Cs, Ga, Hf, Rb, Sr) is summarised.

Naujakasite, Na6(Fe,Mn)Al4Si8O26, long known from the Ilímaussaq alkaline complex, South Greenland, was not reported until 1999 from other occurrences of alkaline rocks in spite of the fact that the mineral is composed of common elements. In 1999, a variety of naujakasite rich in Mn was found in the Lovozero alkaline complex in the Kola Peninsula, Russia. This variety has been approved by the IMA as a new mineral, manganonaujakasite, Na6(Mn0.53Fe2+ 0.47)Al4Si8O26. At Ilímaussaq naujakasite is a rock-forming mineral in the highly evolved rock naujakasite lujavrite in which it may make up more than 75 vol.%; at Lovozero manganonaujakasite is a very rare constituent in mineralised lovozerite–lomonosovite lujavrite. Naujakasite appears to take the place of nepheline in hyper-agpaitic nepheline syenites characterised by exceptionally high Na/K ratios. The nepheline syenites at Ilímaussaq have an average Na/K (atomic) ratio of 3.08, and the naujakasite lujavrites have the extreme ratio 4.56. The nepheline syenites of the Khibina and Lovozero complexes are characterised by lower Na/K ratios, 1.27 for Khibina and 1.67 for Lovozero, and thus nepheline is stable in the hyper-agpaitic rocks and naujakasite occurs only in pegmatites.

In the agpaitic nepheline syenites of the Ilímaussaq complex, analyses by X-ray fluorescence spectrometry reveal that Ge is largely held in arfvedsonite (2.4–4.3 ppm) and aegirine (2.5–4.3 ppm) and has abnormally low contents (down to < 0.2 ppm) in microcline. This distribution is discussed in relation to three controls: (1) increased ratios of octahedral to tetrahedral Ge in Na-rich, Ge-bearing melts and in high-pressure melts, (2) increased ratios of bivalent to quadrivalent Ge in highly reduced melts and (3) reduced admittance of Ge into the structurally ordered low microcline which crystallised in the low-temperature agpaitic magmas.

A study of the whole-rock geochemistry and mineral chemistry of high-TiO2 Upper Jurassic and medium-TiO2 Lower Cretaceous basalts from Kong Karls Land, Svalbard, is presented. Geochemical criteria indicate that the basalts are initial rifting tholeiites with weak signs of crustal contamination. The Upper Jurassic basalts appear to be associated with the Olga Rift, part of a trans-Barents rift system which failed to link the proto-Atlantic and proto-Arctic basins. The Lower Cretaceous basalts may be more closely related to initial rifting tholeiites on Franz Josef Land and Spitsbergen generated during the rifting stage of opening of the Canada Basin. During break-up of the Barents Shelf, the sequence of magma types corresponds to the pre-, syn- and post-rifting stages established in other areas of continental break-up. Evidence for a possible hot-spot or plume trail, extending from Siberia to the Yermak Plateau over 250 Ma, is assembled.

Detailed tephrochronological studies in Kamchatka Peninsula, Russia, permitted documentation of 24 Holocene key-marker tephra layers related to the largest explosive eruptions from 11 volcanic centers. Each layer was traced for tens to hundreds of kilometers away from the source volcano; its stratigraphic position, area of dispersal, age, characteristic features of grain-size distribution, and chemical and mineral composition confirmed its identification. The most important marker tephra horizons covering a large part of the peninsula are (from north to south; ages given in14C yr B.P.) SH2(≈1000 yr B.P.) and SH3(≈1400 yr B.P.) from Shiveluch volcano; KZ (≈7500 yr B.P.) from Kizimen volcano; KRM (≈7900 yr B.P.) from Karymsky caldera; KHG (≈7000 yr B.P.) from Khangar volcano; AV1(≈3500 yr B.P.), AV2(≈4000 yr B.P.), AV4(≈5500 yr B.P.), and AV5(≈5600 yr B.P.) from Avachinsky volcano; OP (≈1500 yr B.P.) from the Baraniy Amfiteatr crater at Opala volcano; KHD (≈2800 yr B.P.) from the “maar” at Khodutka volcano; KS1(≈1800 yr B.P.) and KS2(≈6000 yr B.P.) from the Ksudach calderas; KSht3(A.D. 1907) from Shtyubel cone in Ksudach volcanic massif; and KO (≈7700 yr B.P.) from the Kuril Lake-Iliinsky caldera. Tephra layers SH5(≈2600 yr B.P.) from Shiveluch volcano, AV3(≈4500 yr B.P.) from Avachinsky volcano, OPtr(≈4600 yr B.P.) from Opala volcano, KS3(≈6100 yr B.P.) and KS4(≈8800 yr B.P.) from Ksudach calderas, KSht1(≈1100 yr B.P.) from Shtyubel cone, and ZLT (≈4600 yr B.P.) from Iliinsky volcano cover smaller areas and have local stratigraphic value, as do the ash layers from the historically recorded eruptions of Shiveluch (SH1964) and Bezymianny (B1956) volcanoes. The dated tephra layers provide a record of the most voluminous explosive events in Kamchatka during the Holocene and form a tephrochronological timescale for dating and correlating various deposits.

J. Ravenscroft, M. Gardner, H. J. Luinge, B. Miller, E. A. Maier, D. Smythe-Wright, J. C. Bailey, H. Compaan and G. A. Best, Anal. Proc., 1990, 27, 265 DOI: 10.1039/AP9902700265

The whole-rock geochemistry and mineral chemistry of six samples of Lower Cretaceous tholeiitic basalt from Franz Josef Land, U.S.S.R., have been studied. Geochemical criteria indicate that the basalts are initial rifting tholeiites characterised by low contents of Ti and other H-elements, suggesting derivation from a depleted mantle source. These tholeiites formed during a Lower Cretaceous rifting stage in the formation of the Arctic Ocean basin, most likely the opening of the Canada Basin.

The autonomic nervous system, particularly the sympathetic nervous system, plays an important role in initiating or perpetuating cardiac arrhythmias in various animal models and presumably also in man. The parasympathetic and sympathetic nervous systems interact in a complex manner in regulating the electrophysiologic properties of cardiac tissues. To the extent that a given arrhythmia is influenced by autonomic tone, the alteration in autonomic tone produced by an antiarrhythmic drug will modify the effects of the antiarrhythmic drug. Several antiarrhythmic drugs that are known to have direct electrophysiologic effects on cardiac tissues also reduce efferent sympathetic nerve activity by acting in the CNS. This centrally mediated effect on sympathetic activity likely plays an important role in the antiarrhythmic effects of these drugs. Other antiarrhythmic drugs interact directly with autonomic receptors on cardiac tissues in addition to producing their direct electrophysiological effects. The electrophysiologic effects of such antiarrhythmic drugs that interact with autonomic receptors are qualitatively modified by the magnitude and nature of the prevailing autonomic tone. These interactions between the autonomic nervous system and antiarrhythmic drugs must be kept in mind when the mechanism of action of these drugs is considered.

The purpose of these experiments was to determine whether muscarinic cholinergic agonists exerted a negative chronotropic effect in the absence of endogenous norepinephrine in isolated guinea pig ventricular myocardial strips. The chronotropic response to physostigmine (10(-6) M) in control, reserpine-pretreated animals, and in the presence of increased norepinephrine release induced by superfusion of tyramine (10(-5) M), was studied. The control rates in the control, reserpine-pretreated, and tyramine-treated groups were 106 +/- 40, 93 +/- 31, 109 +/- 28/min, respectively. Propranolol (10(-6) M) produced a 23% slowing in rate in control animals and an 8% slowing in reserpine pretreated animals (P less than 0.01), suggesting basal secretion of norepinephrine. Tyramine (10(-5) M) produced a 28% increase in rate in control animals (P less than 0.05) and tyramine (10(-4) M) produced no increase in reserpine-pretreated animals. Physostigmine produced similar negative chronotropic response in control, reserpine-pretreated, and tyramine-treated groups of 45, 49, and 28%, respectively. Physostigmine produced no change in measured Purkinje fiber action potential characteristics, except for a decreased rate of spontaneous diastolic depolarization. Our results demonstrate that physostigmine slows the spontaneous rate in control, reserpine-pretreated and tyramine-treated groups, indicating that muscarinic cholinergic agonists exert a direct negative chronotropic effect at postjunctional cell surface receptors, independent of the presence or level of adrenergic tone.

The physiologic importance of parasympathetic influence on the sinoatrial and atrioventricular nodes is well established, but the importance of parasympathetic modulation of ventricular function remains controversial. Recognized effects of muscarinic cholinergic stimulation on ventricular automaticity and ventricular repolarization, the ability of muscarinic cholinergic agonists to antagonize catecholamine effects in the ventricle and proposed mechanisms for these effects are described. Anatomic studies have demonstrated a great abundance of cholinergic nerve endings in association with the ventricular conducting system. Stimulation of the vagus nerve or addition of muscarinic cholinergic agonists suppresses ventricular automaticity in most species and antagonizes isoproterenol-induced action potential shortening and isoproterenol-restored slow response action potentials. In vivo, interactions between the parasympathetic and sympathetic nervous systems occur at multiple levels. Muscarinic cholinergic agonists inhibit release of norepinephrine from sympathetic nerve terminals, inhibit catecholamine-stimulated adenylate cyclase activity and alter cyclic guanosine monophosphate (GMP) and possibly cyclic adenosine monophosphate (AMP) levels. Evidence is also presented that, in vivo, parasympathetic effects on ventricular electrical function might influence the pathophysiologic milieu responsible for initiation or termination of certain ventricular arrhythmias. Vagal influences appear to be protective against certain digitalis-induced arrhythmias and protective in certain experimental acute myocardial infarctions. In human beings, there appears to be tonic vagal tone in the ventricle and vagal stimulation terminates certain types of ventricular tachycardia. The evidence presented supports a physiologic role of parasympathetic stimulation in altering ventricular electrical function.

Regulation of the slow inward current appears to be an important mechanism by which the autonomic nervous system modifies cardiac function. Beta-adrenergic stimulation augments the slow inward current by increasing the number of functional slow inward current channels. This effect is mediated by cyclic adenosine monophosphate (cyclic AMP) and presumably involves phosphorylation of membrane proteins associated with the slow channels. Beta antagonists (propranolol) act by inhibiting beta-adrenergic activation of adenylate cyclase and thereby prevent increases in cyclic AMP. The calcium channel antagonists (verapamil) act directly at the level of the slow channels to inhibit the slow inward current independent of changes in cyclic AMP. Cholinergic stimulation attenuates beta-adrenergic stimulation of the slow inward current by one or both of two potential mechanisms: reduction in cyclic AMP formation and antagonism of the distal effects of cyclic AMP.