Clastic dikes in Middle Devonian sandstones of the Gauja Formation, southeastern Estonia/Settesooned Kesk-Devoni Gauja kihistu liivakivides Kagu-Eestis.INTRODUCTION Clastic clastic /clas·tic/ (klas´tik) 1. undergoing or causing division. 2. separable into parts. clas·tic adj. 1. dikes are usually exotic phenomena in bedrock. In compressed sedimentary sequences they may yield specific essential information on the past geological processes that have taken place during the sedimentary breaks. In Baltoscandia, clastic dikes are considerably rare structures in sedimentary sequences and the uppermost parts of the crystalline basement. Sedimentary clastic dikes are formed due to filling of open fractures with allogenic allogenic /al·lo·gen·ic/ (-jen´ik) allogeneic. allogenic, adj from individuals of the same species. Tissue transplanted from one person to another is said to be allogenic. detrital de·tri·tus n. pl. detritus 1. Loose fragments or grains that have been worn away from rock. 2. a. Disintegrated or eroded matter: the detritus of past civilizations. material either on land or in sub-bottom layers of water bodies. Open fractures may be of tectonic tectonic /tec·ton·ic/ (tek-ton´ik) pertaining to construction. or any other origin (e.g. compaction, landslides, etc.) in a rock massif mas·sif n. 1. A large mountain mass or compact group of connected mountains forming an independent portion of a range. 2. subjected to extension or strike-slip movements. Usually filling of fractures soon follows their opening. In fact, filling of these fractures is a specific kind of infracrustal sedimentation in near-surface environments. The filling material was provided either from the Earth's surface or from suspension in the covering water body, from fracture walls or from loose layers of the sequence cross-cut by the fracture. Sedimentary structures (bedding types, etc.) may carry information on within-fracture sedimentation either above or under groundwater level. Clastic dikes may have developed either soon after the formation of the surrounding sediments or after some long period. From the moment of filling of fractures, sedimentary dikes and the surroundings have common diagenesis diagenesis Sum of all processes, chiefly chemical, that produce changes in a sediment after its deposition but before its final lithification. Usually, not all the minerals in a sediment are in chemical equilibrium, so changes in interstitial water composition or in history. However, clastic dikes differing from the surroundings in water permeability may differ in the intensity of respective mineralizations. In northern Baltoscandia, clastic dikes are met in different-age formations from Precambrian to Devonian. Sedimentary clastic dikes in the Precambrian crystalline basement, representing mainly NE-SW-trending tectonic fractures once open but afterwards filled with Cambrian sandstone, are reported from Baltic coastal areas in SW Finland and eastern Sweden (Bergman 1982; Tynni 1982). In the Ordovician carbonate sequence of North Estonia numerous clastic dikes have been found and described (Orviku 1960; Heinsalu & Andra 1975). These dikes are filled with sandy material and strongly cemented by diagenetic pyrite pyrite (pī`rīt) or iron pyrites (pīrī`tēz, pə–, pī`rīts), pale brass-yellow mineral, the bisulfide of iron, FeS2. and carbonates. The clastic dikes in the Precambrian basement and Middle Ordovician The Middle Ordovician (from 472 to 461 million years ago) is the second subdivision of the Ordovician period. During this time warm shallow sea covered much of the land, and was home to a rich diversity of marine life. layers are related to regional sets of fractures in bedrock, mainly of NE-SW direction. The mode of occurrence and processes of formation are, however, specific at each site. The number of Devonian dikes recently found is considerably small. They are observed only in a restricted area of southeastern Estonia where sandstones of the Lode Member of the Gauja Formation are exposed (Fig. IA). In the early 1990s we observed and documented a NW-SE-trending clastic dike A clastic dike is the geological term used to describe a seam of 'foreign' sedimentary material (often breccia) that fills cracks in sedimentary strata. Since sedimentary strata are usually formed by deposition in the horizontal plane, they usually remain in that orientation, of sandy and muddy composition in Piusa quarry. T. Pani PANI Polyaniline PANI Pseudo Automatic Number Identification PANI P-Access-Network-Info explored the whole 500 m long and 150-200 m wide quarry where six clastic dikes were recorded (Fig. 1B; Pani & Mark-Kurik 1995). Recently, Piusa quarry has been a popular subject of geological observations (Sostra 1997). Our study deals with the composition of the Devonian clastic dikes, which is significant for the estimation of their age and possible origin. Laboratory investigations of the sample collection were carried out. [FIGURE 1 OMITTED] GEOLOGICAL SETTINGS Devonian sandstones and carbonate rocks are widely spread in the middle and western parts of the East European Craton The East European craton is the core of the Baltica proto-plate and consists of three crustal regions/segments: Fennoscandia to the northwest, Volgo-Uralia to the east, and Sarmatia to the south. . In southern Estonia ENE-WSW-trending stripes of Middle Devonian In the geological timescale, the Middle Devonian epoch (from 397.5 ± 2.7 million years ago to 385.3 ± 2.6 million years ago) occurred during the Devonian period, after the end of the Emsian age. The Middle Devonian epoch is subdivided into two stages: Eifelian and Givetian. sandstone layers of the Parnu, Narva, Arukula, Burtnieki, Gauja, and Amata formations are exposed. In the SE corner of Estonia Upper Devonian dolomitic dol·o·mite n. 1. A white or light-colored mineral, essentially CaMg(CO3)2, used in fertilizer, as a furnace refractory, and as a construction and ceramic material. 2. marlstones occur (Fig. 1; Kajak 1997; Kleesment & Mark-Kurik 1997). Fracturing of Devonian sandstones is widespread, but not so frequent as in pre-Devonian carbonate rocks. Closed unfilled joints prevail (Miidel 1982; Kleesment & Pirrus 2000; Pirrus at al. 2002). Filled fractures--clastic dikes--have been found in sandstones of the Gauja Formation in Piusa (Fig. 1B) and neighbouring Tabina sandstone pits only. No vertical displacements are observed in connection with the dike-bearing fractures. The maximum thickness of the Gauja Formation is about 80 m. The formation is dominated by weakly to medium-cemented light to yellowish-grey, rarely light brown, pinkish-brown or variegated variegated adjective Multifaceted; with many colors, aspects, features, etc fine-grained cross-bedded sandstones. In the sequence of the formation two cyclic members can be distinguished. The lower complex, the Sietin Member, is mostly represented by sandstones with a layer of grey or variegated siltstone siltstone Hardened sedimentary rock that is composed primarily of angular silt-sized particles (see silt) and that is not laminated or easily split into thin layers. in its topmost part. The lower part of the thicker (50-60 m) upper complex, the Lode Member, consists of light, mainly white sandstones. Siltstones and clays dominate in its upper part. The Gauja Formation is overlain o·ver·lain v. Past participle of overlie. by the up to 30 m thick Amata Formation consisting of sandy-silty sediments alternating with frequent clay interbeds. The Amata Formation is overlain by the dolomitic complex of the Upper Devonian Plavinas Formation; (Kleesment 1995; Kajak 1997; Kleesment & Mark-Kurik 1997). The Lode time of the Gauj a age was the phase of maximum Middle Devonian regression in the area under consideration. Subaqueous and subaerial delta plains alternated during this time, reflecting near-shore environments of retreating sea. Evidences of gradually changing depositional environments are imprinted into the sandstone sequence. Lenticular lenticular /len·tic·u·lar/ (len-tik´u-ler) 1. pertaining to or shaped like a lens. 2. pertaining to the lens of the eye. 3. pertaining to the lenticular nucleus. goethite-enriched interlayers of conglomerate often occur, in which clasts of siltstone and silty silt n. A sedimentary material consisting of very fine particles intermediate in size between sand and clay. v. silt·ed, silt·ing, silts v.intr. claystone are enclosed into sandy matrix. The high maturity of mineralogical composition and high content of kaolinite kaolinite (kā`əlĭnīt), clay mineral crystallizing in the monoclinic system and forming the chief constituent of china clay and kaolin. in mud fraction hints at the processes of subaerial weathering in the source area (Kurss 1992; Kleesment 1995, 1997; Plink-Bjorklund & Bjorklund 1999). The clastic dike-bearing Lode Member is exposed in large Piusa and Tabina quarries and in the banks of the Piusa River valley between these quarries (Fig. IA). The 12 kin long section displays 17 natural high scarps with a total length of about 900 m. The frequency of fractures in these rocks is considerably higher than in the underlying Devonian complexes (Kleesment & Pirrus 2000). On average, a fracture was observed in each 2.8 m. Two joint systems (striking WWN-EES and NNE-SSW) dominated. A few synclinal syn·cli·nal adj. 1. Sloping downward from opposite directions to meet in a common point or line. 2. Geology Relating to, formed by, or forming a syncline. Adj. 1. deformations occur there as well (Fig. 2A). Gauja sandstone beds are slightly dislocated dis·lo·cate tr.v. dis·lo·cat·ed, dis·lo·cat·ing, dis·lo·cates 1. To put out of usual or proper place, position, or relationship. 2. also in river banks. A few local faults show throws up to 20 cm. These are within-formational dislocations, covered with intact horizontal beds, and are probably caused by early compaction of sediments. [FIGURE 2 OMITTED] The Piusa-Tabina area is located within the SE marginal zone The marginal zone is the region at the interface between the non-lymphoid red pulp and the lymphoid white-pulp of the spleen. (Some sources consider it to be the part of red pulp which borders on the white pulp, while other sources consider it to be neither red pulp nor white pulp. of the gentle slope of the Fennoscandian Shield where the sedimentary cover forms a uniform Estonian Homocline (Puura & Vaher 1997). The dipping of bedding planes is around 15". However, the location is very near or within the marginal zone of the Haanja-Petseri branch of cupola-type anticlinal structures, which belong to the regional Liepaja-Riga-Pskov system of Late Caledonian compressional dislocations (Indans 1962; Kaplan & Hasanovitch 1969; Puura & Vaher 1997). Those were recurrently activated during the Devonian (Suveizdis 1979; Vaher et al. 1980; Puura & Vaher 1997). FIELD OBSERVATIONS AND SAMPLING In walls of 500 m long and up to 200 m wide Piusa quarry about 100 fractures were measured. Most of them are closed. Fractures trending NW-SE and steeply dipping NE dominate. Meridional me·rid·i·o·nal adj. Of or relating to meridians or a meridian. (N-S) and NE-SW trending fractures are less numerous (Fig. 1B). In most cases they dip 60[degrees] to 90[degrees] towards NW or NE. Among closed fractures, least numerous are SW and SE dipping fractures. Observation of fractures in quarries is hampered by talus talus (tā`ləs), deposit of rock fragments detached from cliffs or mountain slopes by weathering and piled up at their bases. A talus is a common geologic feature in regions of high cliffs. , hiding large areas of walls. In 1990 a clastic dike was discovered at two sites of the southern wall of Piusa quarry (Fig. 1B). In 1995-2001, filled fractures Fl-F4 (Figs. 1B, 2B, 3A) and a single similar dike Dike, in Greek religion and mythology Dike: see Horae. dike, in technology dike, in technology: see levee. dike Bank, usually of earth, constructed to control or confine water. (Fig. 3B) were observed and sampled in Piusa and Tabina, respectively. Clastic dike 1 as the most representative structure (Figs. 1B and 2) was carefully cleaned and described in 1995. Its best 7 m high exposure is located in the southeastern wall of Piusa quarry and trends in the direction NW 300[degrees] at a dip of 84[degrees] to SW. In 1990 the horizontal extent of the southern surface was fragmentarily frag·men·tar·y adj. Consisting of small, disconnected parts: a picture that emerges from fragmentary information. frag observable along the southern wall of the quarry, stretching for about 100 m (Fig. 1B). The 9.5-10 cm wide dike is composed of sandy material consisting of abundant clasts of sandstone, siltstone, and claystone, resembling the rocks of the Gauj a Formation. No stratification was found in the dike. The dike attracts attention by its rusty-brown pigmentation pigmentation, name for the coloring matter found in certain plant and animal cells and for the color produced thereby. Pigmentation occurs in nearly all living organisms. and stronger cementation cementation In geology, the hardening and welding of clastic sediments (those formed from preexisting rock fragments) by the precipitation of mineral matter in the pore spaces. It is the last stage in the formation of sedimentary rock. rate than in the surrounding rocks. The fracture walls are covered with goethite goethite Widespread iron hydroxide mineral, α-FeO(OH), the most common ingredient of iron rust. In terms of relative abundance, it is second only to hematite (α-Fe2O3) among iron oxides. film. Samples (Pil-Pi7a) were taken from every metre of the dike. Reference samples from the Gauj a Formation (Pill, Pi 13), outcropping in the quarry walls, and from the overlying overlying suffocation of piglets by the sow. The piglets may be weak from illness or malnutrition, the sow may be clumsy or ill, the pen may be inadequate in size or poorly designed so that piglets cannot escape. Quaternary quaternary /qua·ter·nary/ (kwah´ter-nar?e) 1. fourth in order. 2. containing four elements or groups. qua·ter·nar·y adj. 1. Consisting of four; in fours. deposits (Pi8) were also collected (Fig. 2B, Tables 1-6). Clastic dike 2 composed of sandy material is exposed in the uppermost 1.5 m of the quarry wall, 60 m northeast of F1 (F2; Figs. 1B and 2A). The 10 cm wide dike trends in the direction NW 300[degrees] at a dip of 86[degrees] NE. No bedding structures were found. Clastic dikes F1 and F2 are located in the SE side of a small synclinal structure, which is about 4 m deep and 40 m wide (Fig. 2A). Its axial axial /ax·i·al/ (ak´se-al) of or pertaining to the axis of a structure or part. ax·i·al adj. 1. Relating to or characterized by an axis; axile. 2. plane trends in the direction WNW WNW abbr. west-northwest Noun 1. WNW - the compass point midway between west and northwest west northwest 285[degrees] at a dip of 75[degrees] SW. The syncline is roughly parallel to fractures F1 and F2. A horizontal layer of Quaternary deposits rests on the top of the almost smooth bedrock. Clastic dike 3 is exposed in the northern part of the NE wall of the quarry (F3; Fig. 1B). Trending in the direction NW 297[degrees] at a dip of 88[degrees] SW, it consists of two parallel thin dikes 1-3 cm wide. The filling is clayey silty and sandy material, abundantly impregnated im·preg·nate tr.v. im·preg·nat·ed, im·preg·nat·ing, im·preg·nates 1. To make pregnant; inseminate. 2. To fertilize (an ovum, for example). 3. with goethite (Fig. 3A). The goethite films on the fracture walls are uneven. The observable vertical extent of this clastic dike is 4 m. On the opposite wall of the quarry a closed vertical fracture of the same direction was discovered (Fig. 1B). Clastic dike 4 was found in the northwestern wall of the quarry. It trends in the direction NW 320[degrees] (F4; Fig. 1B) and its observable vertical reach is 5 m. The 5 cm wide fracture is filled with unbedded silty sandstone containing abundant small angular clayey-silty clasts. The fracture filling is relatively strongly cemented compared to the surrounding sandstone in the quarry wall. In Tabina quarry (Fig. IA), numerous closed fractures cut the wall. In the eastern wall of the quarry only a single clastic dike was found. It trends in the direction WNW 280[degrees] at a dip of 85[degrees] NE. Its observable vertical reach is about 4 m. The 8 cm wide fracture is filled with loose sandstone. The northern surface of the fracture is even, the southern surface slightly uneven. The fracture walls have only a very poor goethite pigmentation, whereas in the fracture filling goethite is a significant component. In the upper part of the exposure, a syncline-like deformation of sandstone beds is observed (Fig. 3B). This syncline is due to thinning of a sandstone bed 1 m down from the top of the bedrock. The material of this layer near the open fracture open fracture n. A fracture in which broken bone fragments lacerate soft tissue and protrude through an open wound in the skin. Also called compound fracture. has fallen into the fracture. [FIGURE 3 OMITTED] LABORATORY TECHNIQUES Laboratory techniques are the sum of procedures used on natural sciences such as chemistry, biology, physics in order to conduct an experiment, all of them follow scientific method; while some of them involves the use of complex laboratory equipment from laboratory glassware to Grain size spectrum of the clastic and detrital material was studied in laboratory using sieving. The mineralogical composition of fractions of samples was determined by means of optical microscopy and X-ray diffraction. The grain size distribution of both the dike and surrounding sandstone, matrix of the clastic dike and disintegrated clasts separated from the dike sandstone, and the content of clasts in dikes were studied (Tables 1-3). Clasts were carefully separated from poorly and moderately cemented samples and studied (Fig. 4A). In some cases sandy clasts with predominantly kaolinite cement, sandy clasts with kaolinitegoethite cement, and clasts from clayey silt were separately analysed (Table 2). Soft clasts of some samples were crumbled to the matrix by laboratory works and the clastic dike was investigated in total (Table 1, samples Fil imp. 1. imp. os> of Fall, v. i. os> Fell. and Fi12). Separated clasts were fractionated using sieves with diameters of 10, 7, 5, 3, and 2 mm. From the < 2 mm fraction mud (<0.01 mm) was removed by washing. The grain size interval of 2-0.01 mm was separated by sieving into 2.0-1.0, 1.0-0.5, 0.5-0.25, 0.25-0.1, 0.1-0.05, and 0.05-0.01 mm fractions. The three coarsest fractions were investigated using binocular binocular, small optical instrument consisting of two similar telescopes mounted on a single frame so that separate images enter each of the viewer's eyes. As with a single telescope, distant objects appear magnified, but the binocular has the additional advantage optical microscope optical microscope See under microscope. . The 0.1-0.05 mm fraction was further separated and classified using bromoform. Heavy and light minerals were determined in immersion liquids under a microscope in plane-polarized transmitted light. About 300-500 mineral grains were counted in each mineral spectrum and the results were expressed as percentages (Tables 4-6). [FIGURE 4 OMITTED] The mineralogical composition of muddy particles (<0.01 mm) in clastic dikes was studied by X-ray diffraction using HZG4 diffractometer A Diffractometer (Main Entry: dif·frac·tom·e·ter Pronunciation: di-"frak-'tä-m&-t&r Function: noun) is a measuring instrument for analyzing the structure of a usually crystalline substance from the scattering pattern produced when a beam of radiation or particles (as X rays or (Fe filtered Co radiation). Sample powder was mixed with alcohol and spread on the glass slide (slurry slurry, n a thin mixture of insoluble material floating in liquid. slurry solids in suspension. Used as a method of feeding pigs—slurry is pumped through fixed lines and delivered to troughs by hoses equipped with gasoline pump fittings. mounts were prepared). For identification of the main minerals a range from 5[degrees] to 40[degrees] 2[tjeta] was step-scanned (step size 0.05[degrees] 2[theta Theta A measure of the rate of decline in the value of an option due to the passage of time. Theta can also be referred to as the time decay on the value of an option. If everything is held constant, then the option will lose value as time moves closer to the maturity of the option. ], counting rate 3 s). In mud fraction also trace elements Trace elements A group of elements that are present in the human body in very small amounts but are nonetheless important to good health. They include chromium, copper, cobalt, iodine, iron, selenium, and zinc. Trace elements are also called micronutrients. were examined by X-ray fluorescence using the equipment VRA-30 (X-ray tube Fe filtered Co radiation, with Mo anode anode (ăn`ōd), electrode through which current enters an electric device. In electrolysis, it is the positive electrode in the electrolytic cell. anode Terminal or electrode from which electrons leave a system. at 50 kV and 15 mA). Peak/background ratios were used for calibration. The precision of analysis was estimated as follows: 5 ppm for U, Th, Pb, Y, Sr, Rb, Br, Se, and As; 10 ppm for Zn and Ni; 50 ppm for Mn; and 0.3% for [Fe.sub.2][O.sub.3]. RESULTS OF LABORATORY STUDIES Lithology li·thol·o·gy n. 1. The gross physical character of a rock or rock formation. 2. The microscopic study, description, and classification of rock. of clastic dikes Out of four clastic dikes sampled, the most detailed information was obtained from dike Fl, from which 10 samples were analysed (Figs. 2B, 4; Tables 1, 2, 4-6). Dike Fl consists mainly of fine-grained quartz sand that contains abundant clasts of random orientation (Fig. 4B). The main character of the matrix is similar to the surrounding rocks. A comparatively high content of the muddy component is due to decomposition decomposition /de·com·po·si·tion/ (de-kom?pah-zish´un) the separation of compound bodies into their constituent principles. de·com·po·si·tion n. 1. of clayey-silty clasts (Tables 1 and 3). The content of clasts in the dike varies between 16.6 and 70.6% (Table 1). Poorly sorted isolated clasts did not reveal any internal stratification (Fig. 4B). The diameter of clasts ranges from 2 to 40 mm. Sandy matrix contains also angular particles of clayey silt finer than 2 mm. Angular clasts of variegated clayey siltstone occur together with sub-rounded and rounded clasts of sandstone (Fig. 4C, D). Part of the sandstone clasts contain kaolintte-goethite cement and are pigmented. Part of the clasts are white, having mainly kaolinitic cement only with a little admixture of goethite. Sandstone clasts with goethitic cement are slightly coarser than the white clasts (Table 2). Relatively coarse white sandstone clasts occur in the lower part of the clastic dike. Upwards the amount of clasts of clayey silt increases (Fig. 4A). In the upper part of the dike coarser sandstone clasts often contain small angular particles of clayey silt (Fig. 4D). Host of the clastic dike is weakly cemented except 1 m between samples Pi4 and Pi5 (Fig. 1B), which is moderately cemented. Mainly kaolinite-illite cement contains also goethite and a small amount of gypsum gypsum (jĭp`səm), mineral composed of calcium sulfate (calcium, sulfur, and oxygen) with two molecules of water, CaSO4·2H2O. It is the most common sulfate mineral, occurring in many places in a variety of forms. (Fig. 5). Clastic dike F4 is composed of relatively strongly cemented very fine sandstone, containing abundant angular clasts of variegated clayey silt with chaotic orientation. The diameter of the clasts varies from 2 to 20 mm. The grain-size composition of the filling material corresponds to the mixed silty-sandy sediment (Table 1, sample 12). The fracture in Tabina quarry was filled with loose sandstone. As a whole, in clastic dikes of the studied quarries only fillings with no evidences of water transport-related stratification structures were found. It suggests that the fracture fillings found in Piusa and Tabina quarries were formed above the groundwater level. [FIGURE 5 OMITTED] Mineralogical composition of clastic dikes The mineralogical composition of the 0.1-0.05 mm fraction of clastic dikes is rather close to that of the wall rock sandstones. Quartz is the dominating detrital mineral amounting almost always to 89-97% (Table 4). The quartz content is much lower (16.8%) in the clayey siltstone from the Piusa quarry wall (sample Pi13). At the same time, in clayey silty clasts from fracture F1 with the same grain size distribution (Table 2, samples Pi4cc, Pi6cc, and Pi7a c) the quartz content is similar to the surrounding sandy deposits (Table 4). In the silty mixture of matrix and decomposed de·com·pose v. de·com·posed, de·com·pos·ing, de·com·pos·es v.tr. 1. To separate into components or basic elements. 2. To cause to rot. v.intr. 1. clasts from dike F4 of Piusa quarry (sample Pi12; Fig. 1; Table 4) the quartz content is between the two. In the overlying Quaternary sand above fracture F1, the amount of quartz is considerably lower (sample Pi8). In the Devonian, quartz grains are sub-angular to sub-rounded. Undulous extinction is observable in about 5-10% of grains. In the overlying Quaternary sandstone undulous grains make up more than 20% of the total. In wall rocks the quartz grains are mainly transparent. In fracture fillings 30-40% and in sandstone clasts with goethite cement (samples Pi3csg and Pi6csg) up to 80% of grains are coated with goethitic film. The coatings have typically intense reddish-brown colour. In the Quaternary sandstone the amount of goethite-coated quartz grains is the same--about 70%. The content of orthoclase in all samples varies usually between 3 and 5%. Small amounts of muscovite muscovite: see mica. muscovite or common mica or potash mica or isinglass Abundant silicate mineral that contains potassium and aluminum and has a layered atomic structure. It is the most common member of the mica group. , biotite biotite (bī`ətīt'), iron-rich variety of phlogopite, most abdunant of the mica minerals. biotite or black mica Silicate mineral in the common mica group. , plagioclase plagioclase Any member of the series of abundant feldspar minerals that usually occur as light- to medium-grey-coloured, transparent to translucent grains or crystals. Plagioclase ranges in composition from albite to anorthite. , and microcline microcline: see feldspar. microcline Common feldspar mineral, one form of potassium aluminosilicate (KAlSi3O8) that occurs in many rock types. Green specimens are called amazonstone and may be used as gems. are present. A higher content of micas is registered in silty samples. In Quaternary sandstone (sample Pi8) brown biotite occurs in large amounts. Findings of chalcedony chalcedony (kălsĕd`ənē) [from Chalcedon], form of quartz the crystals of which are so minute that its crystalline structure cannot be seen except with the aid of a microscope. and gypsum are occasional (Table 4). In the heavy mineral spectrum ilmenite ilmenite (ĭl`mĕnīt), black mineral, iron titanium oxide, FeTiO3, crystallizing in the hexagonal system. It is sometimes found as tabular hexagonal crystals but occurs more commonly as small grains in igneous and metamorphic and transparent allothigenic minerals are prevailing in all studied rocks. Due to a higher content of goethite in the matrix of clastic dikes, the content of ilmenite and transparent allothigenic minerals is comparatively low (Table 5). Among heavy transparent minerals of the surrounding rocks and clastic dikes, zircon zircon Silicate mineral, zirconium silicate, ZrSiO4, the principal source of zirconium. Zircon is widespread as an accessory mineral in acid igneous rocks; it also occurs in metamorphic rocks and, fairly often, in detrital deposits. is dominating (40-60%), accompanied by considerable amounts of tourmaline tourmaline (t  r`məlĭn, –lēn), complex borosilicate mineral with varying amounts of aluminum, iron, magnesium, sodium, lithium, potassium, and sometimes other elements, . The rest of the spectrum is composed mainly of the
staurolite-rutile assemblage. Kyanite kyaniteor cyanite or disthene Silicate mineral, one of several phases in the aluminum silicate (Al2SiO5) system. Its colour ranges from gray-green to black or blue, with blue and blue-gray being most common. , garnet garnet, name applied to a group of isomorphic minerals crystallizing in the cubic system. They are used chiefly as gems and as abrasives (as in garnet paper). , monazite monazite (mŏn`əzīt), yellow to reddish-brown natural phosphate of the rare earths, mainly the cerium and lanthanum metals, usually with some thorium. Yttrium, calcium, iron, and silica are frequently present. , and amphibole amphibole (ăm`fəbōl'), any of a group of widely distributed rock-forming minerals, magnesium-iron silicates, often with traces of calcium, aluminum, sodium, titanium, and other elements. are common minerals, while apatite apatite (ăp`ətīt), mineral, a phosphate of calcium containing chlorine or fluorine, or both, that is transparent to opaque in shades of green, brown, yellow, white, red, and purple. , anatase an·a·tase n. A rare blue or light yellow to brown crystalline mineral, the rarest of three forms of titanium dioxide, TiO2, used as a pigment, especially in paint. , titanite ti·tan·ite n. See sphene. , corundum corundum (kərŭn`dəm), mineral, aluminum oxide, Al2O3. The clear varieties are used as gems and the opaque as abrasive materials. Corundum occurs in crystals of the hexagonal system and in masses. , pyroxene pyroxene (pī`rŏksēn), name given to members of a group of widely distributed rock minerals called metasilicates in which magnesium, iron, and calcium, often with aluminum, sodium, lithium, manganese, or zinc occur as X in the chemical , and epidote epidote Any of a group of colourless to green or yellow-green silicate minerals with the general chemical formula A2B3(SiO4)(Si2O7)O(OH), in which A is usually calcium (Ca) and B are rare. Garnet occurs in large amounts in silty sediments and clasts. Clearly different is the mineralogical composition of the Quaternary deposits, where amphibole is the dominating heavy mineral (Pi8, Table 6). The character of zircon and other heavy minerals in clastic dikes, including sandy and silty clasts, and reference rocks is similar. Zircon occurs as subhedral, short-prism, slightly rounded and mainly colourless colourless or US colorless Adjective 1. without colour: a colourless gas 2. dull and uninteresting: a colourless personality 3. grains. In the grain size class of 0.1-0.05 mm the proportion of coloured zircon is about 10%. Brown, pink, and yellow varieties occur almost in equal amounts. Zoned grains account for 10-15%. Permanently, but in minor amounts, multiedged grains are found. Tourmaline is predominantly green; the brown variety constitutes 5-15% of grains. In minor amounts, but permanently, blue tourmaline occurs. Rutile rutile, mineral, one of three forms of titanium dioxide (TiO2; see titanium). It occurs in crystals, often in twins or rosettes, and is typically brownish red, although there are black varieties. is represented mainly by short-prism slightly rounded brown to dark brown grains and a specific greenish-yellow variety with an amount of 25-30%. X-ray diffraction analysis of the studied mineralogical composition of muddy particles showed besides general similarity to the normal composition of reference sandstones also some different features (Fig. 5). The muddy fraction of the sandstones of the Gauja Formation is characterized by a considerably high content of kaolinite accompanied with illite Illite is a non-expanding, clay-sized, micaceous mineral. Illite is a phyllosilicate or layered silicate. Structurally illite is quite similar to muscovite or sericite with slightly more silicon, magnesium, iron, and water and slightly less tetrahedral aluminium and interlayer (sample Pi11 in Fig. 5). In clayey-silty deposits the share of kaolinite is lower and the goethite supplement is characteristic (sample Pi13). The content of kaolinite is about two times smaller in sandy matrix of clastic dikes (samples Pi5 and Pi6) and clasts embedded in it (sample Pi7a c; Fig. 5), indicating that the fine-grained detrital material was partly derived from different sources. This is quite normal as migration abilities of fine material are greater. The occurrence of gypsum in many levels of fracture fillings (samples Pi5 and Pi7a c) is most likely connected with late or even present-day mineralizations. Quaternary sandstone has a clearly different (sample Pi8) composition, where this fraction is represented by a mixture of chlorite chlorite Widespread group of layer silicate minerals composed of hydrous aluminum silicates, usually of magnesium and iron. The name, from the Greek for “green,” refers to chlorite's typical colour. and illite and contains admixture of jarosite (Fig. 5). For the geochemical comparison of clastic dikes and surrounding rocks, quantitative data of ten trace elements in muddy fraction were juxtaposed jux·ta·pose tr.v. jux·ta·posed, jux·ta·pos·ing, jux·ta·pos·es To place side by side, especially for comparison or contrast. (Fig. 6). Geochemically matrix and clasts do not differ substantially from the surrounding bedrock. This is valid for two groups of elements: Rb, Y, and Th that are mainly related to feldspars and other clastic allothigenic minerals, and Mn, Ni, Zn, As, Sr, Pb, and U, which could be carried also by clay minerals and most fine-grained, unspecified authigenic minerals. All Devonian samples, however, differ significantly from a Quaternary sample which is enriched with Mn, As, and Pb, and somewhat depleted de·plete tr.v. de·plet·ed, de·plet·ing, de·pletes To decrease the fullness of; use up or empty out. [Latin d in Rb and Sr. The contents of Rb and Th within the dike are slightly higher, and Mn, Ni, and Y lower than in the surrounding rock. [FIGURE 6 OMITTED] Diagenetic alterations As a whole, mineralogical and chemical data indicate that during the formation of the clastic dike and its subsequent history the authigenic mineralization process was negligible, except its enrichment with goethite. The data presented above reveal that clastic dikes are comparatively enriched with goethite component (Table 5; Fig. 5). Goethite has caused during the post-dike history stronger cementation of clastic dikes as compared to the surrounding rocks. As a result, the cementation rate is most increased in dikes F1 and F4 of Piusa quarry (Fig. 1B). The walls of fracture F1 are covered with a goethitic film (Fig. 7A). Along many bedding surfaces adjoining the fracture, goethite-rich interlayers and pockets were formed, which is illustrated by sample Pi10 (Fig. 7B). On detrital grains goethitic films are formed. The enrichment of sandstone clasts by goethite had a selective character; goethite concentrated mostly in the coarser varieties of sandstone (Tables 2 and 5; samples Pi3csg and Pi6csg). The portion of sandstone clasts in which kaolinitic cement is partially replaced by goethite is higher in the upper part of the fracture filling (Fig. 4A). Formation of goethite due to groundwater filtration is common in Devonian sandstones. [FIGURE 7 OMITTED] Fractures cutting the Devonian sandstone complex increase significantly the permeability of rocks and provide pathways for migration of fluids. Diagenetic changes in clastic dikes differ from those of the wall rock. In the fillings selective dissolution has taken place and the replacements of clay minerals can occur. In the clasts made up of clayey silt the micas were replaced by clay minerals. While in the reference rocks clayey silt consists mainly of mica minerals in the light fraction and green biotite among heavy minerals (sample Pi13), in clasts with the similar grain size (samples Pi4cc, Pi6cc, and Pi7a c) the content of micas is noticeably lower (Tables 4 and 5). These diagenetic changes have been continuing up to the present. Cementation by gypsum took place in the late phase of diagenesis and was possibly induced by replacement of authigenic pyrite or infiltration from the overlying Upper Devonian sulphate-bearing deposits. DISCUSSION AND CONCLUSIONS The exact stratigraphical extension of bedrock emplacing the clastic dikes of the Piusa-Tabina area is not firmly established. However, if the above hypothesis of the formation of the observed small synclinal folds is correct, the base of the fracturing should be deep below the Piusa quarry bottom level. On the other hand, the most probable source of clasts in the dikes was the flatland surface with specific arid-type eluvial sediments. It means that many tens of metres would be the minimum vertical extent of the once open fractures. Clastic dikes have been observed only in poorly cemented sandstone of the upper part of the Gauja Formation. Furthermore, they are always accompanying fold-like deformation structures in Devonian bedrock. The formation of fold-like structures and sporadically placed sections of open fractures are likely the results of the same compressional deformation phase, which could coincide with the aerial land uplift in the Haanja-Petseri branch of the regional Liepaja-Riga-Pskov dislocation dislocation, displacement of a body part, usually a bone. When a bone is dislocated, the ends of opposing bones are usually forced out of connection with one another. In the process, bruising of tissues and tearing of ligaments may occur. zone (Puura & Vaher 1997). An evidence of locally changing deformation rate is the WNW-SEE-trending clastic dike F3 in Piusa quarry, which within the 200 m stretch thins out to the closed fracture (Fig. 1B). In general, the strike of clastic dikes and synclines WNW 280-320[degrees] coincides with the respective fracture system WNW 290-320[degrees] in the Lode Member of the Gauja Formation. The composition of clastic dikes is of special interest for estimating the provenance prov·e·nance n. 1. Place of origin; derivation. 2. Proof of authenticity or of past ownership. Used of art works and antiques. level in the geological section (Fig. 8). Clasts in dikes include rare complex, clast-in-clast varieties (Fig. 4D) and well-rounded strongly cemented sandstone pebbles, suggesting the existence of cemented and already once redeposited beds on the source surface. Such continental, eluvial, and temporary watering-evaporation-related sediments could form due to on-land processes in arid Devonian climates. The conglomerate layer in the Gauja-Amata transition (Fig. 8) could be a representative of such sediments. [FIGURE 8 OMITTED] The high clast content, poor sorting, numerous angular clasts, and absence of bedding (Fig. 4B) suggest that the fracture fillings were deposited by rapid mass flows in subaerial conditions. Despite the little age difference between the sedimentation and fracturing, the walls of open fractures stayed stable. The sandstone beds had to be lithified enough to survive even surfaces of filled fractures. No indicative fossils are found in clastic dikes. Thus, the biostratigraphic age of the dikes remains unknown. Lithological and mineralogical data suggest that infilling immediately followed the formation of fractures. The lack of any material reminding of beds younger than the Gan a Formation suggests that the clastic dikes formed during Gauja time. Taking into consideration the total sequence of the Gauja Formation, and the position of Piusa quarry in it, the possible source level for the filling material, Gauja-Amata transition beds, was located some 20-30 m higher than the present-day bedrock surface (Fig. 8). The Gauja Formation is covered by the up to 20 m thick sandy Amata Formation, followed by carbonate deposits of the Plavinas Stage (Fig. 8). The lack of carbonate clasts indicates that no material has been derived from the Plavinas Stage. Regarding the palaeohydrogeological conditions of dike formation and their development during the Late Palaeozoic to Cenozoic history, the above data allow some speculative conclusions. If our construction about the subaerial formation of fracture fillings at depths more than 20-30 m is correct, the sea-level drop had to be more than these figures. It suggests a considerably high stand of the land surface above sea level. A tectonic uplift Tectonic uplift is a geological process most often caused by plate tectonics which increases elevation. The opposite of uplift is subsidence, which results in a decrease in elevation. Uplift may be orogenic or isostatic. event at the end-Gauja time could be an explanation. However, already in Amata time and the Late Devonian In the geological timescale, the Late Devonian epoch (from 385.3 ± 2.6 million years ago to 359.2 ± 2.5 million years ago) occurred during the Devonian period, after the end of the Givetian age. The first tetrapods appeared in the Late Devonian, circa 365 Ma. , the area with dikes was submerged under sea level. During the Late Palaeozoic to Cenozoic, the fluid-flow regime in the explored deposits was greatly affected by fractures, cross-cutting the poorly lithified sandstones of the Gauja Formation, which at least temporarily served as an aquifer aquifer (ăk`wĭfər): see artesian well. aquifer In hydrology, a rock layer or sequence that contains water and releases it in appreciable amounts. . The fractures were highly permeable permeable /per·me·a·ble/ (per´me-ah-b'l) not impassable; pervious; permitting passage of a substance. per·me·a·ble adj. That can be permeated or penetrated, especially by liquids or gases. conduits for vertical flow of fluids. Watered and dry episodes of the rock massif alternated in the history, depending on the altitudes and relief of the territory. Iron-rich fluids precipitated goethite cement into the fracture fillings. The conditions during diagenesis differed in fracture fillings from the wall rock. In the fillings transformations of clay minerals and replacement of micas by clay minerals took place. During the late stage of diagenesis, in near-surface conditions certain new replacements and changes occurred. Due to alteration of authigenic pyrite, a minor content of gypsum cement formed. The whole complex of geological and lithological observations and characteristics of grain-size, mineralogical, and trace element studies suggest that there is no relationship between clastic dikes and the overlying Quaternary deposits. The clastic dikes and also synclinal disturbances are of pre-Quaternary, most probably of late Middle Devonian age. The sources of the fracture fillings were soft disintegrated Devonian sandstone and clasts of Devonian, primarily lithified sandy and silty sediments of Gauj a age. AKNOWLEDGEMENTS We acknowledge the constructive criticism and suggestions by I. Tuuling, U. Sostra, E. Pirrus, and L. Ainsaar. We are also grateful to I. Puura for linguistic improvements, K. Ronk for drawings, and G. Baranov for taking photos. We thank E. Pirrus, U. Sostra, T. Marss, and G. Baranov for permission to use their photos. The study was financed by the research projects Nos. 0332088s02 and 0180551s98 of the Ministry of Education of Estonia and grants Nos. 4417 (to V. Puura) and 4157 (to A. Shogenova) of the Estonian Science Foundation. Received 6 May 2002, in revised form 18 July 2002 REFERENCES Bergman, L. 1982. Clastic dikes in the Aland Islands, SW Finland, and their origin. Geol. Surv. Finland Bull., 317, 8-33. Heinsalu, U. & Andra, H. 1975. Jointing in Oil-Shale Basin and Geophysical Research Methods for Its Study. Valgus valgus /val·gus/ (val´gus) [L.] bent out, twisted; denoting a deformity in which the angulation is away from the midline of the body, as in talipes valgus. The meanings of valgus and varus are often reversed. , Tallinn (in Russian). Indans, A. P. 1962. Tektonicheskaya struktura Latvii. Izd. Akademii nauk Latv. SSR (Scalable Sampling Rate) See AAC. SSR - Scalable Sampling Rate , Riga (in Russian). Kajak, K. 1997. Upper Devonian. In Geology and Mineral Resources of Estonia (Raukas, A. & Teedumae, A., eds.), pp. 121-123. Estonian Academy Publishers, Tallinn. Kaplan, A. & Hasanovitch, K. 1969. On the question of tectonic development of the Lokno High. In Voprosy regional'noj geologii Pribaltiki i Belorussii (Volkolakov, F. G., ed.), pp. 101-113. Riga (in Russian). Kleesment, A. 1995. Lithological characteristics of the uppermost terrigenous ter·rig·e·nous adj. Derived from the land, especially by erosive action. Used primarily of sediments. [From Latin terrigena, earth-born : terra, earth; see ters- Devonian complex in Estonia. Proc. Estonian Acad. Sci. Geol., 44, 221-233. Kleesment, A. 1997. Devonian sedimentation basin. In Geology and Mineral Resources of Estonia (Raukas, A. & Teedumae, A., eds.), pp. 205-208. Estonian Academy Publishers, Tallinn. Kleesment, A. & Mark-Kurik, E. 1997. Middle Devonian. In Geology and Mineral Resources of Estonia (Raukas, A. & Teedumae, A., eds.), pp. 112-121. Estonian Academy Publishers, Tallinn. Kleesment, A. & Pirrus, E. 2000. Fracture systems in Devonian sandstones, South Estonia Proc. Estonian Acad. Sci. Geol., 49, 284-293. Kurss, V. M. 1992. Devonskoe terrigennoe osadkonakoplenie na Glavnom devonskom pole. Zinatne, Riga (in Russian). Miidel, A. 1982. On the interdependence between the fracturing of the Devonian rocks and the direction of the valley of the Vohandu River at its middle course (South Estonia). ENSV TA Toim. Geol., 31, 80 (in Russian). Orviku, K. K. 1960. On the lithostratigraphy lith·o·stra·tig·ra·phy n. 1. Stratigraphy based on the physical and petrographic properties of rocks. 2. Interpretation of the physical characters of sedimentary rocks. of the Volkhov and Kunda stages of Estonia. ENSV TA Geol. Inst. Uurimused, V, 45-88 (in Russian). Pani, T. & Mark-Kurik, E. 1995. Piusa klaasiliivakaevandus. In Liivimaa geoloogia. Ekskursioonijuht (Ainsaar, L. & Kirsimae, K., eds.), pp. 14-15. Tartu, TU, EGS EGS European Geophysical Society EGS European Graduate School EGS El Goonish Shive (webcomic) EGS Environmental Goods and Services EGS Employment Guarantee Scheme (UK) EGS EOS Ground System . Pirrus, E., Kleesment, A. & Soot, M. 2002. Joint systems in Devonian sandstones in the Kiidjarve-Taevaskoda research area, Southeast Estonia. Proc. Estonian Acad. Sci. Geol., 51, 121-132. Plink-Bjorklund, P. & Bjorklund, L. 1999. Sedimentary response in the Baltic Devonian Basin to postcollisional events in the Scandinavian Caledonides. GFF GFF Gain Flattening Filter (used in Erbium Doped Fiber Amplifier) GFF Glass Fiber Filter GFF Grain Foods Foundation GFF Generic File Format (application data) GFF Government Furnished Facility , 121, 79-80. Puura, V. & Vaher, R. 1997. Cover structure. In Geology and Mineral Resources of Estonia (Raukas, A. & Teedumae, A., eds.), pp. 167-177, Estonian Academy Publishers, Tallinn. Sinisalu, R. 1997. Imara-Tabina liivaleiukoha geoloogilisest uurimisest. EGK Aastaraamat 1996. Tallinn, 85-86. Suveizdis, P. I. (ed.). 1979. Baltic Tectonics. Mokslas, Vilnius (in Russian). Sostra, U. 1997. Tektoonilised maakoorerikked Piusa karjaaris. Eesti Loodus, 6, 268-269. Tynni, R. 1982. On Paleozoic microfossils in clastic dikes on the Aland Islands. Geol. Surv. Finland Bull., 317, 36-115. Vaher, R. M., Raukas, A. V. & Tavast, E. H. 1980. The influence of tectonics and bedrock topography on the formation on insular insular /in·su·lar/ (-sdbobr-ler) pertaining to the insula or to an island, as the islands of Langerhans. in·su·lar adj. Of or being an isolated tissue or island of tissue. heights at Estonia. Geomoiphologiya, 3, 55-65 (in Russian). Anne Kleesment (a), Vaino Puura (b), and Toivo Kallaste (a) (a) Institute of Geology at Tallinn Technical University, Estonia pst. 7, 10143 Tallinn, Estonia; kleesmen@gi.ee (b) Institute of Geology, University of Tartu At different times during its history the University of Tartu was known as Academia Gustaviana, University of Dorpat, '' Universität (zu) Dorpat, University of Yuryev, and Tartu State University (Tartu Riiklik Ülikool)''. , Vanemuise 46, 51014 Tartu, Estonia
Table 1. Lithological composition of samples from fracture fillings
Sample Content of Grain size (mm) distribution of matrix, %
No. clasts, % 2-1 1-0.5 0.5-0.25
Pi1 Decomposed 0.1 0.6 11.7
Pi2 26.7 - 0.4 17.1
Pi3 16.8 - 0.3 12.3
Pi4 53.6
Pi5 18.0 <0.1 0.3 11.0
Pi6 28.5 <0.1 0.3 6.9
Pi7 43.2
Pi7a 70.6 0.3 1.5 7.5
Pi8 59.6 3.0 8.4 33.5
Pi12 Decomposed 0.1 0.6 5.2
Pi14 2.7 0.3 0.5 4.5
Tab1 Absent - 1.3 23.5
Sample Grain size (mm) distribution of matrix, %
No. 0.25-0.1 0.1-0.05 0.05-0.01 <0.01
Pi1 61.3 9.8 4.9 11.6
Pi2 62.3 9.7 2.5 8.0
Pi3 69.6 10.8 3.4 3.6
Pi4 Not analysed
Pi5 67.4 11.9 3.5 5.9
Pi6 61.0 16.4 5.7 9.7
Pi7 Not analysed
Pi7a 46.5 18.6 10.5 15.1
Pi8 43.6 6.2 2.0 3.3
Pi12 24.1 14.3 25.3 30.4
Pi14 15.4 10.8 10.1 58.4
Tab1 60.6 9.5 2.0 3.1
Pi, samples from Piusa quarry; Tab, Tabina quarry.
Table 2. Grain size (mm) distribution of decomposed clasts from
fracture Fl of Piusa (Pi) quarry
Sample Character Distribution, %
No. of clasts >1 1-0.5 0.5-0.25
Pi3c All clasts - - 4.2
Pi3csk White - <0.1 2.7
sandstone
Pi3csg Sandstone - <0.1 7.7
with
goethite
Pi4cc Clayey silt <0.1 0.1 1.0
Pi6csk White - <0.1 7.8
sandstone
Pi6csg Sandstone - <0.1 7.0
with
goethite
Pi6cc Clayey silt <0.1 <0.1 1.0
Pi7a c All clasts 0.2 0.2 1.3
Sample Distribution, %
No. 0.25-0.1 0.1-0.05 0.05-0.01 <0.01
Pi3c 28.9 15.0 20.3 31.6
Pi3csk 30.6 36.1 23.4 7.2
Pi3csg 42.4 27.0 15.5 7.4
Pi4cc 8.0 12.6 21.7 56.5
Pi6csk 36.0 25.8 20.7 9.8
Pi6csg 44.4 24.0 13.7 9.9
Pi6cc 7.6 13.2 25.1 53.1
Pi7a c 9.6 7.7 7.3 73.7
Letters by sample numbers denote: c, all clasts; csk, sandstone
clasts with kaolinite cement; csg, sandstone clasts with goethite-
kaolinite cement; cc, clasts of clayey silt.
Table 3. Grain size (mm) distribution of bedrock in studied
locations
Sample
No. Sample location
Pi10 Pocket near F1
Pi11 Sandstone from quarry wall
Pi13 Clayey siltstone from wall
Pi128 Sandstone from mine nearby
Pi129 Sandstone from mine nearby
Pi130 Sandstone from mine nearby
Pi131 Sandstone from mine nearby
Pi132 Sandstone from mine nearby
Pi133 Sandstone from mine nearby
Tab21 Sandstone from quarry wall
Tab22 Sandstone from quarry wall
Tab23 Sandstone from quarry wall
Tab24 Sandstone from quarry wall
Tab25 Sandstone from quarry wall
Sample Distribution, %
No. >1 1-0.5 0.5-0.25 0.25-0.1
Pi10 0.7 0.2 1.9 11.0
Pi11 - 0.1 2.3 89.7
Pi13 - 0.5 2.3 5.0
Pi128 - 2.9 31.1 49.3
Pi129 - 2.5 32.2 50.8
Pi130 - 0.1 6.6 77.5
Pi131 - 1.3 28.9 48.1
Pi132 - 0.8 15.2 75.4
Pi133 - 1.2 49.9 43.8
Tab21 - 0.2 11.2 80.1
Tab22 <0.1 0.7 21.4 71.5
Tab23 - <0.1 3.2 76.0
Tab24 0.3 5.0 42.1 47.6
Tab25 <0.1 1.0 27.1 67.5
Sample Distribution, %
No. 0.1-0.05 0.05-0.01 <0.01
Pi10 4.9 12.6 69.4
Pi11 6.7 0.3 0.9
Pi13 17.3 21.7 53.1
Pi128 15.0 0.9 0.8
Pi129 13.5 0.6 0.4
Pi130 14.6 0.6 0.6
Pi131 18.6 2.3 0.8
Pi132 7.6 0.8 0.2
Pi133 4.9 0.1 0.1
Tab21 5.2 3.3
Tab22 3.5 2.9
Tab23 16.1 4.6
Tab24 2.7 2.3
Tab25 2.3 2.1
Pi, Piusa quarry; Tab, Tabina quarry. Data on samples
Tab21-25 from Sinisalu (1997).
Table 4. Mineral composition (%) of studied samples. Light minerals
of grain size class 0.1-0.05 mm
Sample Quartz Orthoclase Plagioclase Microcline
Matrix of fracture fillings
Pi1 89.3 7.4 0.3 -
Pi2 94.0 3.9 0.6 0.3
Pi3 94.0 4.5 0.3 -
Pi5 93.7 2.7 0.9 -
Pi6 92.5 6.3 0.3 0.9
Pi7a 91.9 4.5 0.6 0.3
Pi8 80.9 5.7 0.9 -
Pi12 67.6 5.3 0.3 0.3
Pi14 90.8 5.1 0.8 -
Tab1 89.0 8.0 0.6 -
Clasts
Pi3c 96.7 2.7 - -
Pi3csk 94.4 4.7 - -
Pi3csg 97.3 1.2 0.3 0.6
Pi4cc 92.6 3.4 0.3 -
Pi6csk 97.0 2.4 - -
Pi6csg 97.3 2.4 - -
Pi6cc 96.1 2.1 - -
Pik7a c 93.2 3.7 - 0.1
Surrounding bedrock
Pi10 89.5 4.2 - -
Pi11 93.9 4.9 0.3 -
Pi13 16.8 2.8 - -
Pi128 97.8 2.0 0.2 -
Pi129 97.2 2.8 - -
Pi131 98.5 1.5 - -
Pi132 91.1 7.8 0.3
Pi133 95.1 4.6 - 0.3
Tab21 92.4 6.7 - -
Tab22 95.0 5.0 - -
Tab23 94.2 4.2 - -
Tab24 83.6 13.9 - -
Tab25 87.1 11.3 - -
Sample Muscovite Biotite Biotite
(brown) (green)
Matrix of fracture fillings
Pi1 0.7 - 2.0
Pi2 0.3 - 0.3
Pi3 0.9 - 0.3
Pi5 1.5 - 0.3
Pi6 - - -
Pi7a 2.1 - 0.6
Pi8 - 12.2 0.3
Pi12 12.2 0.6 13.7
Pi14 2.5 0.8 -
Tab1 2.1 - -
Clasts
Pi3c 0.3 - -
Pi3csk - - 0.9
Pi3csg 0.3 - 0.3
Pi4cc 0.3 - 3.4
Pi6csk 0.3 - 0.3
Pi6csg - - 0.3
Pi6cc 0.3 - 1.5
Pik7a c 1.3 - 1.7
Surrounding bedrock
Pi10 0.6 0.9 4.8
Pi11 0.3 - -
Pi13 38.8 0.3 41.3
Pi128 - - -
Pi129 - - -
Pi131 - - -
Pi132 0.5 - 0.3
Pi133 - - -
Tab21 0.9 - -
Tab22 - - -
Tab23 1.1 0.5
Tab24 2.0 0.5
Tab25 1.4 0.2
Sample Chalce- Weathered Gypsum
dony micas
Matrix of fracture fillings
Pi1 0.3 - -
Pi2 0.6 - -
Pi3 - - -
Pi5 0.6 - 0.3
Pi6 - - -
Pi7a - - -
Pi8 - - -
Pi12 - - -
Pi14 - - -
Tab1 0.3 - -
Clasts
Pi3c 0.3 - -
Pi3csk - - -
Pi3csg - - -
Pi4cc - - -
Pi6csk - - -
Pi6csg - - -
Pi6cc - - -
Pik7a c - - -
Surrounding bedrock
Pi10 - - -
Pi11 0.3 0.3 -
Pi13 - - -
Pi128 - - -
Pi129 - - -
Pi131 - - -
Pi132 - - -
Pi133 - - -
Tab21 - - -
Tab22 - - -
Tab23 - - -
Tab24 - - -
Tab25 - - -
Location of samples from Piusa (Pi) quarry is shown in Figs. 1
and 2. Explanation of letters by clast sample numbers is given in
Table 2. The character and location of reference rocks are given
in Table 3. Data on samples from Tabina quarry Tab21-Tab25 are
from Sinisalu (1997).--not found.
Table 5. Mineral composition (%) of investigated samples. Heavy
minerals of grain size class 0.1-0.05 mm
Sample Total Biotite Biotite Chlorine
content of (brown) (green)
heavy
minerals
Matrix of fracture fillings
Pi1 0.44 0.6 0.9 0.6
Pi2 0.45 - 3.0 0.4
Pi3 0.73 - 0.4 0.2
Pi5 0.42 - 0.6 0.2
Pi6 0.17 - 0.6 -
Pi7a 0.50 - 0.7 0.4
Pi8 3.80 1.2 4.0 -
Pi12 0.79 <0.1 29.0 2.2
Pi14 0.70 - 1.0 -
Tab1 0.50 0.2 3.0 1.1
Clasts
Pi3c 0.42 - 5.0 0.6
Pi3cs1 0.40 <0.1 0.4 0.2
Pi3csg 0.55 0.4 8.0 0.4
Pi4cc 2.80 <0.1 6.4 -
Pi6cs1 0.48 0.2 0.4 0.2
Pi6csg 0.50 - 1.4 -
Pi6cc 5.60 <0.1 1.2 -
Pi7a c 1.10 0.2 3.3 0.4
Surrounding bedrock
Pi10 5.10 <0.1 14.6 -
Pi11 0.67 - <0.1 0.2
Pi13 0.30 0.4 47.0 2.2
Pi128 0.10 - 0.7 -
Pi129 0.53 - 0.2 -
Pi131 0.87 - - -
Pi132 1.11 - 0.2 -
Pi133 1.38 - 0.2 -
Tab21 3.10 - - -
Tab22 2.90 - - -
Tab23 0.65 - - -
Tab24 1.79 0.8 -
Tab25 4.50 0.1 -
Sample Muscovite Carbonite Sphalerite
Matrix of fracture fillings
Pi1 - - -
Pi2 - 0.2 -
Pi3 0.4 - -
Pi5 - - -
Pi6 - - -
Pi7a - - -
Pi8 - - -
Pi12 0.6 - -
Pi14 0.4 - -
Tab1 - - -
Clasts
Pi3c - - -
Pi3cs1 <0.1 <0.1 -
Pi3csg - - -
Pi4cc - - -
Pi6cs1 - 0.2 -
Pi6csg - - -
Pi6cc - - -
Pi7a c - - -
Surrounding bedrock
Pi10 - - -
Pi11 - 0.4 -
Pi13 6.0 <0.1 -
Pi128 - - -
Pi129 - - -
Pi131 - - -
Pi132 - - -
Pi133 - - -
Tab21 2.6 0.1 -
Tab22 1.1 0.1 0.1
Tab23 3.4 - -
Tab24 1.7 0.1 -
Tab25 0.6 - -
Sample Baryte Pyrite Goethite
Matrix of fracture fillings
Pi1 - 0.2 16.0
Pi2 - - 13.4
Pi3 - - 7.0
Pi5 - - 18.6
Pi6 - - 15.8
Pi7a - - 23.4
Pi8 - - 11.4
Pi12 - - 16.4
Pi14 0.6 16.2 19.6
Tab1 0.2 13.7 32.6
Clasts
Pi3c - - 26.4
Pi3cs1 - 0.4 20.2
Pi3csg - 0.4 39.6
Pi4cc - - 80.8
Pi6cs1 - - 19.2
Pi6csg - - 29.4
Pi6cc - - 85.2
Pi7a c - - 60.4
Surrounding bedrock
Pi10 - - 72.0
Pi11 - - 1.8
Pi13 4.6 - 16.0
Pi128 - - 1.8
Pi129 - - 3.6
Pi131 - - 11.3
Pi132 - - 4.3
Pi133 - - 14.7
Tab21 - - 6.5
Tab22 - - 14.1
Tab23 - - 11.0
Tab24 - - 15.4
Tab25 0.2 - 1.4
Sample Leucoxene Ilmenite Transparent
heavy
minerals
Matrix of fracture fillings
Pi1 9.6 37.8 32.8
Pi2 5.6 45.4 32.0
Pi3 5.2 48.4 38.4
Pi5 6.4 41.0 33.2
Pi6 13.4 43.4 26.8
Pi7a 8.7 37.1 29.7
Pi8 1.0 19.3 63.1
Pi12 3.0 30.7 18.1
Pi14 3.2 37.0 22.0
Tab1 3.4 27.8 18.0
Clasts
Pi3c 9.6 38.0 20.4
Pi3cs1 5.8 41.2 31.8
Pi3csg 2.0 30.2 19.0
Pi4cc 3.8 4.4 4.6
Pi6cs1 25.2 32.8 21.8
Pi6csg 11.6 36.2 21.4
Pi6cc 2.8 6.8 4.0
Pi7a c 10.7 13.4 11.6
Surrounding bedrock
Pi10 3.4 5.2 4.8
Pi11 7.2 55.4 35.0
Pi13 - 18.8 5.0
Pi128 7.4 64.5 25.6
Pi129 8.0 65.0 23.2
Pi131 8.5 60.7 19.5
Pi132 16.3 54.1 25.1
Pi133 8.5 51.8 24.8
Tab21 9.8 36.5 44.5
Tab22 15.0 22.2 47.4
Tab23 16.7 23.9 45.0
Tab24 11.4 29.0 41.6
Tab25 13.2 35.4 49.1
Location of samples from Piusa (Pi) quarry is shown in Figs. 1
and 2. Explanation of letters by sample numbers is given in Table 2.
The character and location of reference rocks are given in Table 3.
Data on samples from Tabina quarry Tab21-Tab25 are from Sinisalu
(1997).--not found.
Table 6. Mineral composition (%) of investigated samples.
Transparent heavy minerals of grain size class 0.1-0.05 mm
Sample Zircon Tourmaline Garnet Staurolite
No.
Matrix of fracture fillings
Pi1 54.8 15.6 11.0 2.9
Pi2 60.8 16.9 0.3 7.5
Pi3 61.3 17.7 1.8 6.5
Pi5 52.5 24.2 1.4 9.3
Pi6 58.9 16.5 - 9.8
Pi7a 45.5 26.7 4.8 6.7
Pi8 19.4 1.0 4.2 1.0
Pi12 57.6 18.4 0.7 7.6
Pi14 67.5 16.8 - 6.3
Tab1 63.1 16.8 1.1 7.1
Clasts
Pi3c 62.6 14.8 0.3 4.3
Pi3csk 48.2 27.3 4.7 4.7
Pi3csg 57.2 23.6 - 8.2
Pi4cc 41.9 38.2 2.4 3.8
Pi6csk 48.1 25.6 3.2 5.8
Pi6csg 56.4 22.2 - 7.2
Pi6cc 49.5 30.3 1.5 6.7
Pi7a c 39.0 24.9 17.9 5.2
Surrounding bedrock
Pi10 55.7 19.6 0.9 11.1
Pi11 35.6 32.4 1.6 12.6
Pi13 45.9 26.3 7.3 4.4
Pi128 27.7 36.7 0.5 24.0
Pi129 62.3 16.2 0.7 7.0
Pi131 47.0 35.8 0.5 4.4
Pi132 44.7 21.7 0.7 23.0
Pi133 41.2 28.0 2.1 17.7
Tab21 64.1 3.8 0.7 6.6
Tab22 67.7 3.4 0.2 7.4
Tab23 49.2 9.5 0.7 6.7
Tab24 60.4 7.9 0.3 12.4
Tab25 66.8 4.0 0.5 8.5
Sample Kyanite Rutile Titanite Anatase
No.
Matrix of fracture fillings
Pi1 0.5 5.3 <0.1 -
Pi2 1.6 7.5 - 0.6
Pi3 0.6 6.5 0.4 0.4
Pi5 0.2 6.3 - 0.2
Pi6 0.7 9.4 - -
Pi7a 3.0 7.3 - 1.8
Pi8 0.6 1.6 - -
Pi12 1.3 9.2 1.0 -
Pi14 0.5 5.8 - -
Tab1 - 5.4 - -
Clasts
Pi3c 0.9 9.9 - -
Pi3csk 0.8 4.0 - -
Pi3csg - 7.3 - -
Pi4cc 0.5 7.5 0.5 -
Pi6csk 1.3 6.4 - -
Pi6csg 0.7 7.2 0.7 0.4
Pi6cc - 6.7 - 0.5
Pi7a c 0.4 6.0 - 0.3
Surrounding bedrock
Pi10 1.8 6.1 - -
Pi11 1.8 8.2 - 0.2
Pi13 0.6 7.9 - -
Pi128 1.8 3.6 0.5 0.7
Pi129 - 7.4 - -
Pi131 - 6.4 - -
Pi132 2.0 2.6 - 0.7
Pi133 2.4 3.3 - 0.4
Tab21 0.4 20.9 - 1.2
Tab22 0.5 17.0 - 1.8
Tab23 0.3 32.4 - 0.8
Tab24 2.4 12.4 - 1.9
Tab25 1.1 17.9 - -
Sample Weathered Monazite Xenotime Apatite
No. Ti-
minerals
Matrix of fracture fillings
Pi1 3.3 1.4 - 0.2
Pi2 3.2 1.3 - -
Pi3 1.6 2.6 - -
Pi5 4.1 0.6 - -
Pi6 2.8 1.7 - -
Pi7a 2.4 1.2 - -
Pi8 0.4 0.8 - 0.8
Pi12 1.3 1.6 0.3 0.3
Pi14 1.0 1.6 - 0.5
Tab1 1.6 0.5 - -
Clasts
Pi3c 5.5 1.7 - -
Pi3csk 2.0 1.2 - -
Pi3csg 2.7 0.5 - -
Pi4cc 1.9 1.4 - 0.5
Pi6csk 2.6 1.9 - 0.6
Pi6csg 2.2 1.5 - -
Pi6cc 1.9 - - 0.5
Pi7a c 2.0 0.7 0.2 -
Surrounding bedrock
Pi10 0.6 0.6 - -
Pi11 4.0 0.8 0.2 2.2
Pi13 4.7 0.6 - -
Pi128 0.9 1.3 - 0.5
Pi129 1.8 2.1 0.4 -
Pi131 1.0 2.9 - -
Pi132 1.3 2.0 - -
Pi133 1.6 2.1 0.4 -
Tab21 - 0.6 - -
Tab22 - 1.2 - 0.4
Tab23 - 0.4 - -
Tab24 - 1.1 - -
Tab25 - 0.6 - -
Sample Corundum Amphibole Pyroxene Epidote
No.
Matrix of fracture fillings
Pi1 - 5.0 - -
Pi2 - 0.3 - -
Pi3 - 0.6 - -
Pi5 - 1.2 - -
Pi6 - - - -
Pi7a - 0.6 - -
Pi8 - 69.4 0.8 -
Pi12 - 0.7 - -
Pi14 - - - -
Tab1 - 2.2 2.2 -
Clasts
Pi3c - - - -
Pi3csk - 7.1 - -
Pi3csg - 0.5 - -
Pi4cc - 1.4 - -
Pi6csk - 4.5 - -
Pi6csg - 1.5 - -
Pi6cc - 2.4 - -
Pi7a c - 3.2 0.1 0.1
Surrounding bedrock
Pi10 - 3.6 - -
Pi11 - 0.4 - -
Pi13 - 2.2 - -
Pi128 0.5 1.3 - -
Pi129 - 0.7 1.4 -
Pi131 - 0.5 1.5 -
Pi132 - 1.3 - -
Pi133 - - 0.8 -
Tab21 0.2 - 1.1 0.4
Tab22 - - 0.2 0.2
Tab23 - - - -
Tab24 0.6 0.2 - 0.4
Tab25 - - 0.2 0.4
Location of samples from Piusa (Pi) quarry is shown in Figs. 1
and 2. Explanation of letters by sample numbers is given in Table 2.
The character and location of reference rocks are given in Table 3.
Data on samples from Tabina quarry Tab21-Tab25 are from Sinisalu
(1997).--not found.
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