FORMATION OF THE CRUSTAL MELTING LAYER AND ITS RELATIONS TO THE DEFORMATION OF CONTINENTAL CRUST:AN EXAMPLEFROM SOUTHEAST CHINA

Unlike the magma intrusion model,the in- situ melting hypothesis advanced in the lastdecade regards the upper crustas a closed system,and granite as the resultof the materialswithin system changing from order (protolith) to disorder (melts) and to new order(granite) with the variations of entropy of the system.The various geological and geochemi-cal data from the Mesozoic granitesof southeast China are explained logically and systemical-ly by the hypothesis,concluding that they should be originated from the melting of pro-toliths.According to the hypothesis,melts generated from in- situ melting are of layer- likewithin the crustand batholithsare the protruding parts of the uppersurface of the layer (de-fined as the Melting Interface,MI for short) .On the basis the author tries to discuss thesource of heatfor the Mesozoic crustal melting in southeast China.

Gupeiite Body in the Siberian Taiga (the Zone of Passage of the Tunguska Meteorite and the Vitim Bollid)

Many years have passed since the two cosmic bodies of the Tunguska meteorite and the Vitim bollid fell to Earth, but so far the substance of these bodies has not been found on Earth. Therefore, each metal body found on the territory of their passage is of particular interest. The body of iron silicide weighing 12 kg was studied, which was accidentally discovered by a hunter of the village of Kyker in the Siberian taiga on the right bank of the Nercha River, Tungokochensky district, Trans-Baikal Territory. Coordinates of the place of discovery are: 53º19'N lat, 116º19'E long. The territory is located in the zone of the passage of the Tunguska meteorite and the Vitim bollid, 25 km from the hunting village of Green Lake. The body is named “Ilekta” after the nearest stream flowing into the Nercha River. The composition and magnetic properties of the exotic find have been determined. It is established that its main mass is composed of iron silicide, gupesiite Fe3Si (zussite?) and contains inclusions of needle-like rhabdite. On the surface, the body is covered with a melting crust, with signs of boiling, a bubbly structure and a film of clay minerals of terrestrial origin. In the molten porous crust, eutectic-schreibersite-gupeiite is observed, and rare titanium carbide crystals are also noted. The magnetic susceptibility of the samples is not uniform (286.6 - 461.8 10-6E-06 m3/kg). It is assumed that a drop of melt separated from the flying space body, and experienced overheating and boiling of the surface layer in the dense layers of the atmosphere.

Tonalites and plagiogranites of the Char suture-shear zone in East Kazakhstan:Implications for the Kazakhstan-Siberia collision

The paper presents first Ue Pb zircon ages and geochemical data from Carboniferous granitoids（tonalites and plagiogranites） of the Char sutureeshear zone in East Kazakhstan, which is located in the northwestern Central Asian Orogenic Belt（CAOB）. The study included analysis of geological setting, major and trace elements, and rock petrogenesis. The Char tonalites and plagiogranites occur as NW-striking linear chains inside Visean serpentinite mélange. Petrographycally, the tonalites show signs of syntectonic deformation, and the plagiogranites are less deformed suggesting their later intrusion. The tonalites yielded a LA-ICP-MS zircon age of ca. 323 Ma, i.e. exactly at the boundary between the early and late Carboniferous. Compositionally, the tonalites and plagiogranites are characterized, respectively, by high SiO2（67-70 and 73-74 wt.%） and Al2O3（17-19 and 14-15 wt.%）, Sr/Y 〉 40 and low Yb=0.2-0.5 ppm.Their multi-element patterns show clear Nb-Ta negative anomalies. The low Nb/Ta ratios（7-15） and Zr（114-191 ppm） suggest a MORB-type protolith（amphibolite） with subchondritic Nb/Ta（8-17） and low Zr（1-72 ppm）. The low contents of K and Rb suggest weak assimilation of the melts by island arc felsic crust. The subchondritic Nb/Ta ratios exclude their derivation by the melting of subducted/dehydrated MORB. We argue that the Char high-Al tonalites and plagiogranites formed by the melting of hydrated MORB at the base of the mafic lower crust at pressures of 10-15 kbar. The occurrences of the Char tonalites and plagiogranites inside the Visean serpentinite mélange overlapped by Serpukhovian conglomerates, their alignment parallel to deformation zones, and their geochemical features suggest their origin by the melting of mafic lower crust in relation to the collision of the Siberian and Kazakhstan continents.