bF?U��d�ʂ{���{`@Xdx$�)`��D��1��A|�y��Jfh� ���L�|�PRw�a9�O��9tQ�x�L�i��] � \�?k�~�Ӳ�M��:�7쫴��*N4�K�$�@��Ȇc��lt���MI���=�D�HNJ=B'01��p�E��a���+�[`�����K�2! Many of the clasts are themselves breccias, giving the rock a “breccia-in-breccia” texture. Unit nAai1 is the main unit of the Auclair Formation. Microstructures of prograde mineral growth in the Bushveld aureole This page contains supplementary material for the paper Assessing the extent of disequilibrium and overstepping of prograde metamorphic reactions in metapelites from the Bushveld Complex aureole, South Africa, by D J Waters and D.P. Biotite and sericite define a strong mineral lineation while relicts of magmatic flow layering, poikiloblastic texture, poeciloblastic texture, sieve texture [A texture of metamorphic rocks in which small well-formed crystals of one constituent are enclosed in larger poorly formed crystals of another] poikiloblastische Struktur f Following development of poikiloblastic or dendritic rims, fracturing in biotite appears to mark a fundamental transition from growth to strain of porphyroblasts and a shift from strain focused in the matrix that was accommodating textural sector growth (i.e., as in Fig. *��P��)�?� 353 0 obj <>/Filter/FlateDecode/ID[<371F579CA3033A489E5848863A521DB5>]/Index[326 53]/Info 325 0 R/Length 127/Prev 1032450/Root 327 0 R/Size 379/Type/XRef/W[1 3 1]>>stream Carter 1975; plate 6D, poikiloblastic texture). Biotite grains on the other … Porphyroblasts are a valuable source of information on local tectonic and metamorphic evolution. 10) to transference of some strain to the porphyroblast. Symplectites form from the breakdown of unstable phases, and may be composed of minerals, ceramics, or metals. In general, the breccia clasts are mineral fragments and fragments of rocks with igneous, metamorphic, and breccia texture, and glassy or partially recrystallized melt bodies or fragments thereof. Sample 15299 is a vitric matrix breccia that is probably from a small … endstream endobj startxref YT���J��(l_�*�nP��MQo��%$�\S���kB�~6�֪�(z���,���Kѭ�b� ��Wp��W$�[�b The textures and structures of metamorphic rocks can give insights into physicochemical conditions and the formation and evolution of the earth's continental crust. 26Al-26Mg isotope systematics In hand sample, staurolite frequently occurs as twinned prismatic crystals known as “fairy stones” or “fairy crosses.” In thin section, it displays a poikiloblastic texture which people often liken to vomit spatter—gross, but effective. Poikiloblastic texture, exsolution texture, globular inclusions and exsolved phase has become completely separated and forms an intergranular phase. This formation consists dominantly of hard metasandstone to massive quartzite. 束状变晶结构(sheaf texture):由板状至针状 矿物的发散束状集合体 组成的结构。 变晶之间的包裹关系―― 嵌状变晶结构(poikiloblastic texture) ? �*:Y�-��`��5��;�`a�Sh�0�Bƚ,�kkC�3ۘe���N��� 44). poikiloblastic texture. It has a characteristic pimply surface due to orthopyroxene poikiloblasts. When a magma cools at depth the country rock is warm so the heat loss from the magmatic body is slow, this slow cooling allows the growth of large crystals (phenocrysts) to form, these are often euhedral (well shaped) then the magma is moved into a colder area, this could be the surface or into a dyke or sill. %PDF-1.6 %���� Poikilitic texture similar to that of sample 65015 was also typical of the large boulders at the Apollo 17 site (fig. 326 0 obj <> endobj The deformation involved in the formation of fold-thrust mountain belts generally involves compressional stresses. According to Schreyer (1985), who investigated the same sample, pyrope replaced a preexisting fabric of oriented tourmaline crystals leading to a poikiloblastic texture (Schreyer 1985, their Fig. Here, orange tourmaline and gray K-feldspar include numerous, fine- grained quartzand muscovite mica grains. The extra large size does not mean that they cooled extra slowly. Typical shallow-crustal granites with rapakivi texture are found in the central part (Bogatikov & Birkis 1973), while subvolcanic granophyres occupy large areas in its northern part--on the basement of Ruhnu Island in the Gulf of Riga and in the southwestern part of Saaremaa Island (Kuuspalu 1975; Puura et al. Sample no. ���)���h��׆V�˞�lYڃ2n$@r��Fv)�:��#�~��a��za� Intercalations of blue-grey metapelites or beige, finely laminated siltstones are occasionally present. 1969). �V~�)���Wט��5T�+����y4WS{�Sr�k�R���q��{u�������L9�h��%��o旷�V���;�����>�����ߞ^��Z���4~�=_�T����۩��W��W���~����ch���5�/VxQ�ž�t�~5���Z�_oN/��^^�_�&7�x���z�u>٬��[S���p�����f}������XV�? �z�C"�*e!�U��/�`�6*���W��Dmt���=���n����uqO jd/Q��Sך�������1�`j�Z&�l��Lv)��L ���[���@%�DX�O���T壓�� M� l}w�Q ��Q)Dڑ�u��`��C�?I;d���;�4,oa�h� granoblastic to poikiloblastic. Sample 72275 is a friable fragmental breccia from the edge of the Serenitatis basin. A pegmatitic texture is one in which the mineral grains are exceptionally large. Typical shallow-crustal granites with rapakivi texture are found in the central part (Bogatikov & Birkis 1973), while subvolcanic granophyres occupy large areas in its northern part--on the basement of Ruhnu Island in the Gulf of Riga and in the southwestern part of Saaremaa Island (Kuuspalu 1975; Puura et al. In general, the breccia clasts are mineral fragments and fragments of rocks with igneous, metamorphic, and breccia texture, and glassy or partially recrystallized melt bodies or fragments thereof. Some of the porphyroblasts have inclusions of plagioclase and biotite which make them poikiloblastic in texture. The latter two minerals occur as blocky porphyroblasts ranging from 50 to 100 μm in diameter, and andradite can display poikiloblastic texture. At the beginning of melting pyroxene grains develop spongy border zones (Kleeman et al. These spongy 14). The most obvious evidence of partial melting is the presence of interstitial glass, usually containing tiny quench crystals of skeletal olivine or augite, plagioclase, and oxides (fig. This term describes the inclusions of other minerals within the porphyroblast. The relationship between gneisses from the Kola Superdeep Borehole and their surface analogues Poikiloblastic mafic granulite Poikiloblastic mafic granulite also occurs as elongate bodies trending east-northeast, 10 to 50m wide and 100’s of meters long (Figure 2). In a poikilitic or poikiloblastic texture, the crystal that encloses the chadacrysts. These amphiboles are zoned in cross‐polarized light photomicrographs and back‐scatter electron images (Figures 2d and 2h and 3h). Poikiloblastic texture describes porphyroblasts which are riddled with finer grained inclusions of other minerals. The nucleation energy for this texture seems to be relatively high, but once a nucleus was forrned, it must have grown very rapidly. 2R 2R-5 to 2R-8 These spongy Poikiloblastic: Large, metamorphic grains that enclose numerous small inclusions; analogous to poikolitic igneous texture. https://encyclopedia2.thefreedictionary.com/poikiloblastic. The amphibole forms xenoblastic to sub- idioblastic (sub-prismatic) grains ranging in size from 0.2 mm to 0.3 mm (medium grained). There is rimming of pyroxene by amphibole .