Winchite and the actinolite–glaucophane miscibility gap
Leake et al.1 have recently emphasized the apparent scarcity of winchite s.l., NaCa(Mg, Fe2+)4(Al, Fe3+) [Si8O22/(OH)2] (ref. 2), an amphibole intermediate in composition between the glaucophane–riebeckite series of high-pressure blueschists and the tremolite–actinolite series of lower-pressure greenschists. The rarity of winchite is considered consistent with the existence of a miscibility gap3,4 between these two amphibole series at the metamorphic P–T conditions normally attained in nature. Here we present optical and X-ray properties of Mg- and Al-rich winchite from Venezuela and draw attention to several other recent winchite analyses. In fact, as Schliestedt's5 new data on co-existing sodic and calcic amphiboles in blueschists show, only the present Mg–Al-rich winchite definitely lies within the above miscibility gap.
Alkali amphiboles intermediate in composition between actinolite and riebeckite
Alkali amphiboles of an intermediate composition in the magnesioriebeckite-eckrite series have been found in the metamorphic terrane of Leros Island. A complete compositional gradation has been demonstrated by a series of electron microprobe scans and analyses of spots. Electron microscopic examination revealed no exsolution.The present analyses and other data indicate a closing of the Na-Ca amphiboles gap towards the magnesian end members at temperatures higher than that usually associated with the blueschist facies.
PLEASURE, POWER, AND THE PURSUIT OF COMMUNISM: SOVIET YOUTH AND STATE-SPONSORED POPULAR CULTURE DURING THE EARLY COLD WAR, 1945-1968
art, with certain students accused of “showing political immaturity, failing to understand the Party’s positions on art.” This episode constituted part of a broader crackdown on abstract art by the Khrushchev administration from late 1962, precipitated the the Soviet leader’s derision of such art forms in December 1962 at the Manege exhibit. Such instances demonstrate the limitations of the top-level promotion of youth grassroots initiative, as the Khrushchev leadership reigned in youth autonomy when it threatened to go beyond the boundaries of the permissible. The dates cited above have particular resonance, since both 1957-58 and 1962-63 represent two periods when those at the top of the Party hierarchy moved away from pursuing a more pluralistic, tolerant policy course, due to anxiety inspired by both sharpening Cold War hostilities and domestic developments. In these periods, official rhetoric censured what it labeled as 639 TsAOPIM, f. 635, op. 13, d. 546, ll. 56-57. This is likely related to criticism of the Party associated with the fallout from the Secret Speech and the Hungary invasion. For more, see Polly Jones, “From the Secret Speech to the Burial of Stalin: Real and Ideal Responses to De-Stalinization,” in Jones ed., The Dilemmas, 41-63. 640 TsAOPIM, f. 6083, op. 1, d. 52, ll. 166-67. 641 Susan E. Reid, “In the Name of the People: The Manege Affair Revisited,” Kritika 6.4 (Fall 2005): 673716. 642 On these anxieties, see Dobson, Khrushchev’s Cold Summer, 156-88.