Andesitic Tuff Research Articles

A kácsi bencés apátság román kori kőfaragványai

The Benedictine abbey of Kács dedicated to St Peter was – as historical and archaeological sources suggest – in place of and around the current parish church on top of the hill in the northern part of the village, once the central lands of the Örsúr clan in the 12–13th century. The founders and advowees of the monastery were probably members of the Örsúr clan, who also built a castle on the edge of the village and in nearby Sály. The more exact foundation date of the Benedictine abbey is unknown. Its first mention „monasterium de Kach” is in a diploma of 1248 summarizing the royal land grants to the bishop of Eger. Its title and religious order –„abbas monasterii Sancti Petri de Kach de ordine Sancti Benedicti” – are known from a source of 1292. After 1347 the monastery came to be possessed by a branch of clan named after Tibold and living in nearby Darócz. After the mid-14th century, practically contemporaneously with the breaking up of the clan into branches and the local segmentation of the clan estates, as well as the impoverishment of the monastery, the abbey seems to disappear from the sources. Its demolition in 1549 was before the appearance of the Ottomans around Eger. In place of the ruins a single-nave baroque church was built in the 1720s, which became the parish church of the re-peopled village in the 18th century. In 1882 the western part of the church was enlarged and a tower built in revival romanesque style. The remains were first taken note of in the 1860s by Arnold Ipolyi (1823–1886), the canon of Eger and a researcher of architectural relics of the Árpád Age around Eger. He thought to have found remains of the medieval monastic church in the small baroque church with semi-circular apse. He described several ornamental romanesque stone carvings made from “red stone” (andesite tuff) on the site. Further medieval carvings were found during the extension of the church on the west in 1882, which went to canon Gyula Bartalos’s (1839–1923) collection. Later he gave away these fragments and thus founded the Lapidary of the archiepiscopal Liceum of Eger. In the 1960s excavations were carried on around the parish church of Kács; its archeologist (Károly Kozák) presumed (on the basis of a much-disputed theory) that the floor-plan of the singlenave church with the rounded apse suggests 11th century origin. At the same time, along the south side of the church a narrower nave section terminated also by a semi-circular apse was unearthed, which might rather suggest a 12–13th century three-aisle layout. To the south of this remain, vestiges of a north-south oriented wing were recovered, which can be identified with the Benedictine monastery building with great probability. The paper reviews the romanesque stone carvings found in Kács (which are partly in museums, partly on the spot and some regrettably lost since the 1960s), our art historical knowledge and collection historical data about them. The group of romanesque carved stone relics display stylistic homogeneity. More exact dating within the 12–13th century is hindered by the fragmentary nature and provincial features of the group. Local analogies of the stylistic features, motifs, moulding shapes can be discerned, among other places, in Szomolya, Boldva, Tarnaszentmária and the local stratum of the workshop of Eger cathedral around 1200. On these bases, the studied ensemble is datable to the last third of the 12th century or the beginning of the 13th. The romanesque fragments of Kács inform us of the cultural level and possibilities of a clan who were mainly locally important even in their heyday in the 12–13th centuries as the modest building of their small Benedictine monastery reveals. That is what lends it its significance, too, for in the regional context it is a little known architectural relic of a well-delimited area hallmarked by extant relics of the Árpád Age such as Feldebrő and Tarnaszentmária, the remains of the Benedictine abbey at Boldva and the Cistercian abbey at Bélapátfalva, or the one-time „chef de’oeuvre” of the 12th century, the cathedral of Eger in the centre of the region, rebuilt around 1200.

Geochemistry and petrogenesis of Oligocene volcaniclastic rocks from the Chagai arc: implications for the emplacement of porphyry copper deposits

The Chagai–Raskoh arc is an east–west trending subduction-related magmatic belt in the western part of Pakistan. The initial Cretaceous to Paleocene volcanism in the arc is tholeiitic, and from the Eocene onwards, it becomes calc-alkaline in nature. The Oligocene volcaniclastic rocks are found in the western part of the Chagai–Raskoh arc. These rocks and are mainly andesitic tuffs and belong to the calc-alkaline series. Normalized trace element patterns with negative Nb anomalies and moderate enrichments in K, Sr, Rb and light rare earth elements (LREE) confirm a composition consistent with a continental margin (Andean)-type arc environment. The LREE enriched chondrite-normalized REE patterns with negative Eu anomalies are consistent with their calc-alkaline signature and suggest plagioclase fractionation during differentiation. The Oligocene volcaniclastic rocks from the Chagai–Raskoh arc are more enriched in large ion lithophile elements (LILE) and LREE than the older rocks of the arc. This enrichment in LILEs and LREEs suggests that during the Oligocene–Miocene, more subduction-related fluids were added to the sub-arc mantle source from the subducting Arabian slab and may have been responsible for the porphyry copper deposits in the arc.

Metallogenic model for the Laochang Pb–Zn–Ag–Cu volcanogenic massive sulfide deposit related to a Paleo-Tethys OIB-like volcanic center, SW China

The Laochang Pb–Zn–Ag–Cu volcanogenic massive sulfide (VMS) deposit, located within the Changning–Menglian Paleotethyan suture, SW China, is an economically significant deposit with explored reserves of 866,000 metric tons (t) Pb at 4.5%, 336,000t Zn at 3.3%, 1700t Ag at 155g/t, 116,000t Cu at 0.5–0.9%, 2.84Mt pyrite and accompany 0.8t Au. The deposit comprises three ore clusters (No. I, II and III), each of which comprises dozens of vertically stacked lenticular and stratiform orebodies. Ore clusters I and II within the Early Carboniferous volcano-sedimentary sequence erupted around 320Ma comprise most of the reserves. The Early Carboniferous sequences, situating beside the Laochang caldera, are mainly composed of basaltic to andesitic lavas and volcaniclastic rocks, and divided into three major volcanic cycles. The massive sulfides mostly accumulated in the waning time of the second and third cycles. The orebodies (e.g., orebodies I1+2 and II1) display stockwork and disseminated sulfide ores in the lower part and the semi-horizontal massive sulfide lenses and laminated carbonaceous-sulfidic chert with delicate exhalative-sedimentary textures in the upper part, and they also show vertical metal zonation transiting from Fe–Cu, Cu–Zn–Pb to Pb–Zn–Ag. The underlying rock of the semi-horizontal orebodies has pervasively sericite–pyrite–quartz alteration; comparatively, the overlying is little altered. Ores are dominantly composed of sulfides, lacking sulfate and Fe-oxides, suggesting a very low SO42− concentration in the hydrothermal solution.The host andesitic tuff and basalt show pattern of fractionated rare earth elements (REE) and the enrichment in large ion lithophile elements (LILE; e.g., Rb, Th, U and light REE) and most high field strength elements (HFSE; e.g., Nb, Ta, Hf and Zr). These features are similar to those of oceanic island basalt. The higher REE fractionation and the greater enrichment of LILE (includes light REE) in the andesitic tuffs compared to those in the basalts comply with a fractionational crystallization process in a shallow magma chamber. The δ34S‰ (CDT) of the sulfides ranges from −2.1 to 3.5‰ with an average of 0.2‰. The limited variation of δ34S‰ near zero implies that the sulfur was derived via leaching of the footwall volcanic rocks and/or degassing directly from a magma chamber. Lead isotopic compositions of sulfides also have a small range. The 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb are 18.486–18.684, 15.668–15.712 and 38.725–39.024, respectively, indicating an extremely radiogenic feature similar to the host volcanic rocks. Previous fluid inclusion investigations revealed that ore fluid had high salinity, high temperature and the H–O–C isotopic compositions close to the primary magmatic hydrothermal. Our S–Pb isotopic analysis together with the fluid inclusion study, are supportive to the magmatic degassing genesis for this deposit. The vertical zonation of metal species, occurrence of laminated carbonaceous-sulfidic chert and lack of alteration in the hanging wall imply that the orebodies were formed via seafloor sulfide precipitation instead of sub-seafloor replacement. The occurrence of black shale intercalated with sulfide lenses and the carbonaceous-sulfidic chert caps, especially the absence of sulfate and other oxidized facies in the ores indicate a compelling local anoxic environment for mineral precipitation. This anoxic environment was caused by the venting of magmatic fluids characterized by high temperature, high salinity, metal-charged (Fe, Cu, Pb, Zn and Ag) and H2S-rich. The repetitive activity of magma degassing in the waning stage of volcanic eruption corresponded to the stacked structure of massive sulfide lenses within the top layer in a volcanic cyclothem. The enormous base metal enrichment and highly radiogenic lead isotopes at Laochang are explained to reflect the incorporation of a recycled upper continental crust component into the mantle source for the ore-bearing volcanic rocks during the evolution of Tethyan ocean.

Mineralogical and Geochemical Characteristics and Genesis of the Gülzelyurt Alunite-Bearing Kaolinite Deposit Within the Late Miocene Gödeles Ignimbrite, Central Anatolia, Turkey

AbstractThe Güzelyurt kaolinite deposit is an important source of raw material for the ceramics industry in Turkey. No detailed mineralogical or geochemical characterizations of this deposit have been undertaken previously and these were the goals of the present study. The Güzelyurt alunite-bearing kaolinite occurs along a fault zone in the Late Miocene Gödeles ignimbrite, which consists of dacitic and andesitic tuffs. Horizontal and vertical mineralogical zonations with gradual transitions were observed within the alteration zone. The inner kaolinite, alunite, and 7 Å halloysite zones progress horizontally outward to a smectite zone; and native sulfur- and cinnabar-bearing alunite with 7 Å halloysite and porous silica zones increase as one progresses up through the profile. Fe-(oxyhydr)oxide phases associated with native sulfur and cinnabar demonstrate that multiple hydrothermal-alteration processes resulted in kaolinization and alunitization of the deposit. The kaolinization of feldspar, Fe-(oxyhydr)oxidation of hornblende and mica, the presence of kaolinite as stacked and, locally, book-like forms, and of 7 Å halloysite tubes, and smectite flakes as a blanket on altered volcanic relicts indicate an authigenic origin for this deposit. The leaching of Si + Mg + K and Ba + Rb, the retention of Sr, the enrichment of light rare earth elements relative to the heavy rare earth elements, and the negative Eu anomalies suggest that fractionation of plagioclase and hornblende occurred within the volcanics. The oxygen- and hydrogen-isotopic values of the kaolinite, 7 Å halloysite, smectite, and smectite + kaolinite fractions reflect a steam-heated environment at temperatures in excess of 100°C. An increase in the δD and δ18O values of 7 Å halloysite relative to kaolinite suggests its formation under steam-heated magmatic water, the mixing of steam and meteoric water near the surface, and evaporation. The oxygen- and sulfur-isotopic compositions of alunite suggest the direct influence of steam-derived sulfur. The Güzelyurt alunite-bearing kaolinite deposit is inferred to have formed after an increase in the (Al±Fe)/Si ratio and the leaching of alkali elements, which are driven by the sulfur-bearing low-temperature hydrothermal alteration of feldspar, hornblende, and volcanic glass under acidic conditions within the Neogene dacitic and andesitic tuffs.

EVALUATION OF COPPER DEPOSITS PROSPECT IN WAI WAJO AREA OF SIKKA REGENCY, EAST NUSA TENGGARA PROVINCE

Lowo Deba prospect in Sikka Regency, East Nusa Tenggara Province shows significant evidences for copper deposit. The prospect is discovered by joint cooperation activity between Directorate of Mineral Resources Inventory (DMRI) and Korea Resources Corporation (KORES) in the systematic exploration program. The evaluation based on the quantitative analysis of rock and mineral characteristics as well as geologic mapping, petrography, mineragraphy, fluid inclusion, spectra analysis (PIMA), geochemical and geophysical data. The geology of the prospect area consists of Miocene volcanics of Kiro Formation and Tanahau Formation, intrusion of granodiorite and Quaternary volcanics. The volcanic rock shows the characteristic of tholeiitic magma. The predominant system of lineaments in the prospect area tends to be NE-SW trend. This fault structure appears to have closely relationship with the mineralization in Lowo Deba prospect. The mineralization and alteration outcrops appear to be structural controlled to form epithermal deposit type. Most of the mineralizations are hosted by phyllic – argillic altered andesitic to dacitic tuff which is intruded by granodiorite. Rock samples indicate the mineralization type is quartz vein containing chalcopyrite, galena, sphalerite, covellite and pyrite. The best grade revealed from these altered rocks of 6,980 ppm Cu and 50 ppb Au, and from quartz vein of 4,868 ppm Cu and 57 ppb Au. Mineralization stages evolved from initial higher temperatures (> 320° C) to later lower temperatures (near 170° C). Soil geochemical analysis identify two zones of combined anomaly i.e. Au-Cu-Mo and AgPb-Zn. Those anomalies are concentrated in the phyllic and argillic altered andesitic tuff. These soil anomaly coincide with IP anomalies which are found in electrode separation index of n=5 and n=7 in line WA7 with chargeability value up to 405.7 Msec and resistivity value of 37.7 Ohm-m. In general high chargeability and low resistivity anomalies are developed in the direction of southwest to northeast and still open to the northeast. The high chargeability value allows to predict the occurrence of copper deposits potential. Some bore holes are proposed for the next survey to confirm the presence of new copper deposits in the prospect area.

A Permian andesitic tuff ring at Rožmitál (the Intra-Sudetic Basin, Czech Republic) – evolution from explosive to effusive and high-level intrusive activity

Mafic, monogenetic volcanism is increasingly recognized as a common manifestation of post-collisional volcanism in late Variscan, Permo-Carboniferous intramontane basins of Central Europe. Although identification of individual eruptive centres is not easy in these ancient successions, the Permian Rožmitál andesites in the Intra-Sudetic Basin (NE Bohemian Massif) provide an exceptionally detailed record of explosive, effusive and high-level intrusive activity. Based on field study and petrographic and geochemical data on pyroclastic and coherent rocks, the Rožmitál succession is interpreted as the proximal part of a tuff ring several hundred metres in diameter. Initial accumulation of pyroclastic fall and surge deposits occurred during phreatomagmatic eruptions, with transitions towards Strombolian eruptions. Gullies filled with reworked tephra document periods of erosion and redeposition. Andesitic blocky lavas capped the volcaniclastic succession. Invasion of lavas into unconsolidated sediments and emplacement of shallow-level intrusions in near-vent sections resulted in the formation of jigsaw- and randomly-textured peperites. Most geochemical differences between coherent andesites and pyroclastic rocks can be linked to incorporation of quartz-rich sediments during the explosive eruptive processes and to later cementation of the volcaniclastic deposits by dolomite. The Rožmitál tuff ring could have been one of several phreatomagmatic centres in a monogenetic volcanic field located on an alluvial plain.

The effects of single species, dual species and indigenous mycorrhiza inoculation on citrus growth and nutrient uptake

The objective of this study was to evaluate the effects of selected single arbuscular mycorrhiza (AM) species, dual species inoculations and indigenous mycorrhizae (IM) inoculations, using specific growing media (GM), on the growth and nutrient uptake of sour orange (Citrus aurantium L.) seedlings. Five mycorrhiza species and their dual species inoculations, one commercial and one indigenous (multiple species) mycorrhizae were investigated using two growing media, GM1 (andesitic tuff + peat (1:1, V:V)) and GM2 (andesitic tuff + peat + soil (4 + 5+1, V: V:V)), under controlled greenhouse conditions. The experiments were conducted over 12 months. Mycorrhizal inoculation increased certain plant growth parameters such as shoot height, diameter, and shoot and root dry matter. Generally, mycorrhiza species and their dual species inoculations exerted different responses on plant growth. In GM1, Funneliformis mosseae, Rhizophagus clarus and indigenous mycorrhiza (IM) species were the best inoculants to increase citrus growth, root colonization and nutrient uptake; however, in GM2, Fu. mosseae and IM were the best inocula. Fu. mosseae + R. clarus was the most efficient dual species inoculation in GM1, whereas in GM2 the most efficient combination was Fu. mosseae + Fu. caledonium. The beneficial effects of AM fungi and the dual species inoculation with IM was also significant. Citrus seedlings grew much better in GM1 than in GM2. Root colonization was also increased with dual species inoculation and IM. In addition, the plant phosphorus and zinc content increased with mycorrhizal inoculation. Our results reinforce the efficiency of IM and mycorrhizal inoculations as being as effective as exotic AM fungal isolates. Dual species inoculation and IM show promise in the production of healthy seedlings, using several growing media.

Determination of different growth media and various mycorrhizae species on citrus growth and nutrient uptake

The influence of mycorrhiza species and growing media (GM) on the growth and nutrient uptake of citrus seedlings (sour orange (Citrus aurantium L.)) was studied. The experiments were conducted over 10 months using: four growth media, eight mycorrhiza species, one cocktail of mycorrhizae spores and one indigenous mycorrhiza spore (collected from the citrus orchard rhizosphere). Four different growing media were tested under controlled greenhouse conditions: GM-A, andesitic tuff+peat (1:1, v/v); GM-B, andesitic tuff+compost (1:1, v/v); GM-C, andesitic tuff+peat+compost (2:1:1, v/v/v) and GM-D andesitic tuff+peat+soil (from the Balcalı region) (2:1:1, v/v/v).After a 10 month growing period, the highest values of leaf number, height, shoots and root dry weight were found in GM-C, followed by GM-A and GM-D; whereas the lowest values were found using the GM-B treatment. The results reveal that mycorrhizal inoculation increased the shoot and root dry weight production, compared with the levels found in non-inoculated plants. It was observed that various mycorrhiza species exhibit different responses when varying the growth media; it was also observed that G. clarium, G. margarita, Glomus mosseae, Dr. Kindom (commercial inoculum) and indigenous mycorrhiza (IM) are efficient mycorrhizae species for seedling growth. Mycorrhiza-inoculated citrus seedlings contained a higher content of phosphorus (P), zinc (Zn) than non-inoculated plants.

The Key Tuffite, Matagami Camp, Abitibi Greenstone Belt, Canada: petrogenesis and implications for VMS formation and exploration

The Key Tuffite is a stratigraphic marker unit for most of the zinc-rich volcanogenic massive sulfide deposits of the Matagami Camp in the Abitibi Greenstone Belt. This 2- to 6-m-thick unit was previously interpreted as a mixture of ash fall (andesitic to rhyolitic tuffaceous components) and volcanogenic massive sulfide (VMS)-related chemical seafloor precipitate (exhalative component). Previous attempts to develop geochemical exploration vectoring tools using metal content within the Key Tuffite were mostly inconclusive due to the complex nature of the Key Tuffite unit and a poor understanding of its composition, origin and relationship with the VMS-forming hydrothermal systems. Detailed mapping and thorough lithogeochemistry of the Key Tuffite in the vicinity of the Perseverance and Bracemac-McLeod deposits indicate that the Key Tuffite is a homogeneous calc-alkaline, andesitic tuff that was deposited before the VMS deposits were formed. The unit is mostly devoid of exhalative component, but it is strongly hydrothermally altered close to orebodies. This is characterized by a strong proximal chloritization and a distal sericitization, which grades laterally into the unaltered Key Tuffite. Neither the Key Tuffite nor the ore was formed by seafloor exhalative processes for the two studied deposits. This probably explains why previously proposed exploration models based on metal scavenging proved unsuccessful and suggests that a re-evaluation of the exhalative model should be done at the scale of the mining camp. However, as shown in this study, hydrothermal alteration can be used to vector towards ore along the Key Tuffite.

Stratigraphic, geochemical and U–Pb zircon constraints from Slieve Gallion, Northern Ireland: a correlation of the Irish Caledonian arcs

Recent Ar–Ar and U–Pb zircon geochronology from across the British and Irish Caledonides has revealed a prolonged period of arc-ophiolite formation ( c . 514–464 Ma) and accretion ( c . 490–470 Ma) to the Laurentian margin during the Grampian orogeny. The Slieve Gallion Inlier of Northern Ireland, an isolated occurrence of the Tyrone Volcanic Group, records the development of a peri-Laurentian island arc–backarc and its obduction to an outboard microcontinental block. Although a previous biostratigraphic age constraint provides a firm correlation of at least part of the volcanic succession to the Ca1 Stage of the Arenig ( c . 475–474 Ma), there is uncertainty on its exact statigraphic position in the Tyrone Volcanic Group. Earliest magmatism is characterized by light rare earth element (LREE) depleted island-arc tholeiite. Overlying deposits are dominated by large ion lithophile and LREE-enriched, hornblende-phyric and feldspathic calc-alkaline basaltic andesites and andesitic tuffs with strongly negative ϵNd t values. Previously published biostratigraphic age constraints, combined with recent U–Pb zircon geochronology and new petrochemical correlations, suggest that the Slieve Gallion Inlier is equivalent to the lower Tyrone Volcanic Group. Temporal and geochemical correlations between the Slieve Gallion Inlier and Charlestown Group of Ireland suggest that they may be part of the same arc system, which was accreted at a late stage ( c . 470 Ma) in the Grampian orogeny. A switch from tholeiitic volcanism to calc-alkaline dominated activity within the Lough Nafooey Group of western Ireland occurred prior to c . 490 Ma, some 15–20 Myr earlier than at Tyrone and Charlestown. Supplementary materials: Sampling and geochemical results (major elements, loss on ignition, trace elements, REE and Nd isotopes) are available at www.geolsoc.org.uk/SUP18640 .

Large-scale landslides in Toyama Prefecture, central Japan, and their probable relationship with earthquakes

Large-scale landslides along the Kubusu and Besso rivers in Toyama Prefecture are developed in the Miocene Iwaine Formation, which is composed of andesitic lava, tuff, and tuff breccia. In the middle member of this formation, the tuff is easily altered to montmorillonite-bearing rock, and subsequently plays an important role in the development of landslides events, which tend to be large-scale events, as the massive lava of the upper member forms a cap rock over the tuff. The Kiritani and Koinami basins, which are flat intermontane basins located along the Kubusu and Besso rivers, respectively, are interpreted as landslide-dammed lakes, later filled with sediment. Accelerator mass spectrometry 14C ages show that the landslides forming each dam occurred simultaneously, at approximately 2500 BP. These ages were measured from wood fragments embedded in the landslide material of Kiritani, and from an in situ stump drowned during the impoundment of Koinami. If the trigger of these landslides was an earthquake, it is most likely to have been the penultimate event along the Atotsugawa fault zone.

Geochronology, geochemistry and tectonostratigraphy of Carboniferous strata of the deepest Well Moshen-1 in the Junggar Basin, northwest China: Insights into the continental growth of Central Asia

The Well Moshen-1, the deepest well in the Junggar Basin, is located in the Mosuowan Uplift of the Central Depression. Andesitic magmatic rocks (including the vitric clastic tuff, tuffite and crystal tuff with volcanic–sedimentary rocks) are common in the Carboniferous of the Well Moshen-1. In-situ SHRIMP zircon U–Pb dating and Hf isotope analysis together with geochemical data, seismic profile and magnetic anomaly were carried out on these andesitic tuffs at a depth of 7000m in the Well Moshen-1 in order to reveal the basement character and the evolution of the Junggar Basin and the crustal accretionary process of this region in the Late Paleozoic. By using high-accuracy dating techniques, we obtained the zircon SHRIMP U–Pb age of the andesitic tuff of 331.7±3.8Ma. Geochemical data has also shown that the rocks have typical arc-like geochemical characteristics (low TiO2, Mg#, enrichment in large-ion lithophile elements and depletion in high-field-strength elements, especially Nb, Ta and Ti), suggesting that they are crystallization differentiation products of intra-oceanic arc magmatism. The Carboniferous strata from the Well Moshen-1 are divided into three tectonostratigraphic units with eight periods of volcanic activities, showing a change in the compressional stress of the Mosuowan Uplift from strong to weak and its ending during the Early Permian. The Hf model ages and the formation ages of the zircons from these andesitic tuffs are similar, with 176Hf/177Hf ratios ranging from 0.282906 to 0.283030 and εHf (t) values from 11.7 to 15.2, implying a lateral growth of juvenile crust in the Junggar Basin during the Early Carboniferous. Based on the analysis of regional geologic settings of the Junggar region, the Mosuowan Uplift is considered to be a Carboniferous intra-oceanic arc that resulted from a northward subduction of the South Junggar Ocean, which suggests that the lateral accretion of arcs played an important role in crustal growth in this part of Central Asia.

Evolution of Rajabasa Volcano in Kalianda Area and Its Vicinity, South Lampung Regency

DOI: 10.17014/ijog.v7i1.132Rajabasa Volcano (± 1281 m) and Lampung Tuff, located in the South Lampung Regency, is the main point in order to understand the evolution of Quaternary volcanism in the area. A remote sensing analysis and field geologic work are the methods of the study. The volcanism began with the construction period of the Pre-Rajabasa composite cone which was followed by the destruction period of the cone to form the Pre-Rajabasa Caldera having ca. 25 km in diameter. The present Rajabasa Volcano, along with cones of flank eruptions and monogenesis, has appeared in the Pre-Rajabasa Caldera depression. Those volcanic activities are considered as the second construction period. During the first and the second construction periods, basaltic to andesitic lava flows, pyroclastic breccias, and tuffs were erupted. The Rajabasa eruption points moved in WNW - ESE direction, which were possibly controlled by a subsurface weak zone. The Pre-Rajabasa Caldera erupted voluminous Lampung Tuffs having rhyolite in composition, and they are considered as a combination of pyroclastic falls, flows, and surges, or pyroclastic density currents.

The Arinem Te‐Bearing Gold‐Silver‐Base Metal Deposit, West Java, Indonesia

AbstractThe vein system in the Arinem area is a gold‐silver‐base metal deposit of Late Miocene (8.8–9.4 Ma) age located in the southwestern part of Java Island, Indonesia. The mineralization in the area is represented by the Arinem vein with a total length of about 5900 m, with a vertical extent up to 575 m, with other associated veins such as Bantarhuni and Halimun. The Arinem vein is hosted by andesitic tuff, breccia, and lava of the Oligocene–Middle Miocene Jampang Formation (23–11.6 Ma) and overlain unconformably by Pliocene–Pleistocene volcanic rocks composed of andesitic‐basaltic tuff, tuff breccia and lavas. The inferred reserve is approximately 2 million tons at 5.7 g t−1 gold and 41.5 g t−1 silver at a cut‐off of 4 g t−1 Au, which equates to approximately 12.5t of Au and 91.4t of Ag. The ore mineral assemblage of the Arinem vein consists of sphalerite, galena, chalcopyrite, pyrite, marcasite, and arsenopyrite with small amounts of pyrrhotite, argentite, electrum, bornite, hessite, tetradymite, altaite, petzite, stutzite, hematite, enargite, tennantite, chalcocite, and covellite. These ore minerals occur in quartz with colloform, crustiform, comb, vuggy, massive, brecciated, bladed and calcedonic textures and sulfide veins. A pervasive quartz–illite–pyrite alteration zone encloses the quartz and sulfide veins and is associated with veinlets of quartz–calcite–pyrite. This alteration zone is enveloped by smectite–illite–kaolinite–quartz–pyrite alteration, which grades into a chlorite–smectite–kaolinite–calcite–pyrite zone. Early stage mineralization (stage I) of vuggy–massive–banded crystalline quartz‐sulfide was followed by middle stage (stage II) of banded–brecciated–massive sulfide‐quartz and then by last stage (stage III) of massive‐crystalline barren quartz. The temperature of the mineralization, estimated from fluid inclusion microthermometry in quartz ranges from 157 to 325°C, whereas the temperatures indicated by fluid inclusions from sphalerite and calcite range from 153 to 218 and 140 to 217°C, respectively. The mineralizing fluid is dilute, with a salinity <4.3 wt% NaCl equiv. The ore‐mineral assemblage and paragenesis of the Arinem vein is characteristically of a low sulfidation epithermal system with indication of high sulfidation overprinted at stage II. Boiling is probably the main control for the gold solubility and precipitation of gold occurred during cooling in stage I mineralization.

Analysis of support requirements for a tunnel portal in weak rock: A case study from Turkey

In this paper, engineering geological properties of the entrance portal section of Konakonu Tunnel, located on Black Sea Coastal Highway, Turkey, is studied.Moderately weathered basaltic and andesitic tuffs orderly to be driven by the entrance portal section. Tunnel portal design in weak rock presents some special challenges to the designers, since misjudgements in the design of tunnel can lead to very costly failures. The entrance portal was analyzed by empirical and numerical methods. Both field and laboratory studies were carried out during this study. Field studies involved geological mapping, detailed discontinuity surveying and sampling. Laboratory tests were carried out to determine the physico-mechanical and elastical properties of rock units. For this purpose, tunnel stability analyses were performed at the entrance portal section. The RMR (rock mass rating), Q (rock mass quality), RMi (rock mass index), NATM (new Austrian tunnelling method) and GSI (geological strength index) systems were employed for empirical rock mass quality determination and preliminary tunnel portal support design. The parameters calculated by the empirical methods were used as input parameters for the FEM (finite element method) analysis. The results from the two methods were compared and preliminary support designs were carried out. This comparison suggests that for more reliable support design, empirical and finite element methods should be combined. Key words: Finite element method, rock mass classification systems, tunnel portal, weak rock.

Applicability of excavatability classification systems in underground excavations: A case study

In this study, applicability of the excavatability classification systems in underground excavations is investigated. For this purpose, the entrance portal of the Konakonu (AraklA±-Trabzon) tunnel, excavated in volcanic rocks within the scope of Black Sea coastal highway project, is chosen as pilot study area. The entrance portal of tunnel is excavated through the rocks of Eocene-aged Kabakoy formation of basaltic-andesitic tuffs, aglomerate and basalt. In excavation, basaltic and andesitic tuffs were ripped by using hydraulic breaker; aglomerate and basalt were excavated by using explosives. Based on the results obtained from field and laboratory studies, rock masses are classified in terms of excavatability. According to Pettifer and Fookes (1994), basaltic and andesitic tuffs are included in “hard ripping”, aglomerate and basalt in “blasting required” categories. With reference to Tsiambaos and Saroglou (2009), basaltic and andesitic tuffs fall in “ripping”, agglomerate and basalt in “hammer and blasting” categories. It was found out that the classifications made according to these two methods are completely compatible with in-situ excavation works. Also, it is determined that the parameters give the best results for determining excavation class in underground excavations are GSI (Geological Strength Index), Is (50) (Point load strength index) and If (Discontinuity spacing index). Key words: Blasting, excavatability classification systems, Konakonu tunnel, ripping, underground excavations.

Mineralogical and Geochemical Characteristics and Genesis of Hydrothermal Kaolinite Deposits within Neogene Volcanites, Kütahya (Western Anatolia), Turkey

AbstractThe Kütahya kaolinite deposits are the most important source of raw materials for the ceramics industry in Turkey. To date, no detailed mineralogical or geochemical characterizations of these materials have been carried out; the present study aims to fill that gap. The Kütahya kaolinite deposits formed by alteration of dacite and andesite tuffs related to Neogene volcanism whichwas associated withe xtensional tectonics. The kaolinite deposits contain silica and Fe- and Ti-bearing phases (pyrite, goethite, and rutile) in vertical and subvertical veins that diminish and then disappear upward. Mineralogical zonation outward from the main kaolinite deposit is as follows: kaolinite ± smectite + illite + opal-CT + feldspar; feldspar + kaolinite + quartz + smectite + illite; quartz + feldspar + volcanic glass. The veins and mineral distributions demonstrate that hydrothermal alteration was the main process in the development of the kaolinite deposits of the area. The very sharp, intense, diagnostic basal reflections at 7.2 and 3.57 Å, as well as non-basal reflections, well defined pseudohexagonal to hexagonal crystallinity with regular outlines, ideal differential thermal analysis-thermal gravimetric curves, and ideal, sharp, infrared spectral bands indicate well crystallized kaolinite. Micromorphologically, the development of kaolinite plates at the edges of altered feldspar and devitrified volcanic glass indicates an authigenic origin. Lateral increase in (SiO2+Fe2O3+MgO+Na2O+CaO+K2O)/(Al2O3+TiO2) from the center of the kaolinite deposit outward also indicates hydrothermal zonation. Enrichment of Sr in altered and partially altered rocks relative to freshvolca nic-rock samples demonstrates retention of Sr and depletion of Rb, Ba, Ca, and K during hydrothermal alteration of sanidine and plagioclase within the volcanic units. In addition, depletion of heavy rare earth elements (HREE) relative to light rare earth elements (LREE) in the kaolinized materials may be attributed to the alteration of hornblende. The negative Eu anomaly suggests the alteration of feldspar by hydrothermal fluids. The isotopic data from kaolinite and smectite indicate that hydrothermalalteration processes developed at 119.1–186.9°C and 61.8–84.5°C, respectively. Thus, the kaolinite deposits formed by hydrothermal alteration of volcanic glass, feldspar, and hornblende by a dissolutionprecipitation mechanism which operated under acidic conditions within Neogene dacite, andesite, and tuffs.

Application of Remote Sensing in Monitoring of Faults

The Siyah Bisheh area is located in central part of Alborz zone, 40km south of Amol, Iran. Rock units exposing in the area consists of sedimentary (carbonates, sandstone, siltstone), volcano- sedimentary (andesite to andesitic tuff, tuff), ignimbrite and basalt. when erosion and tectonics have rendered volcanic structures undetectable, remote sensing provides an invaluable tool for their identification, with finding relation between lithology and vegetation is showed that the integrated use of remote sensing techniques and field studies as a powerful tool to distinguish and map the relationships between rock units, structures and alteration zones associated with mineral deposits along the siyah Bishe area. The main image analysis techniques involved in this study were principal component analysis (PCA) and false color composite (FCC). In this study, an anomaly area is distinguished in the southeastern part of the Siyah Bishe area. Hydrothermally altered rocks contain economic mineral deposits whereas unaltered country rocks are non-mineralized. Approximately 5 km2 of the area is underlain by altered rocks, but less than 1 km2 of the altered area contains economic minerals.

GIS를 이용한 경남-울산-부산지역 구성암류의 지질시대별 및 암층별 분포율과 분포특성

암석자원, 산업부지 및 개발계획 등의 지질정보자료로 활용될 수 있도록 분석된 경남, 울산 및 부산지역 구성암류의 지질시대별 암층별 분포율 및 특성은 디음과 같다. 이를 위하여 ArcGIS 9.3, 1 대 250,000 수치지질도 및 수치지형도가 이용되었다. 경남지역의 구성암류는 모두 6개의 지질시대로 구분된다. 분포율은 백악기, 선캠브리아기, 제4기, 쥬라기, 삼첩기 및 제3기의 순으로 감소하고 1.35-57.36%의 범위값을 이루며 그중 전자인 백악기에서 가장 큰 값을 가진다. 구성암층은 모두 40개이며, 그 중 24개가 1.15-13.64%의 다소 좁은 범위 그리고 도합 94.58%를 가져 거의 대부분을 차지한다. 여기에서 가장 우세한 안산암 및 안산암질 응회암은 경남지역의 북동부, 중동부와 남부일대에 발달하며 주변암과 심하게 굴곡진 경계면을 이룬다. 울산지역의 구성암류는 3개의 지질시대로 구분된다. 분포율은 백악기 제4기 및 제3기의 순으로 감소하고 6.90-79.21%의 넓은 범위값을 이루며 전자에서 그 값이 크게 증가한다. 구성암층은 모두 1l개이며, 그 중 9개가 1.50-39.0%의 다소 넓은 범위 그리고 도합 98.63%를 가져 그 대부분을 차지한다. 이 중 가장 우세한 진동층은 울산지역 내측부와 동부 일대에 넓게 발달한다. 부산지역 구성암류는 3개의 지질시대로 구분된다. 분포율은 백악기, 제4기 및 제3기의 순으로 감소하며 6.73-47.02%의 범위값을 이루며 전자 둘에서 88.03%를 가져 그 대부분을 차지한다. 구성암층은 모두 10개이며 그 중 6개가 4.07-47.02%의 넓은 분포범위 그리고 도합 93.02%를 가져 거의 대부분을 차지한다. 이 중 뚜렷하게 우세한 충적층은 낙동강 하류, 서낙동강 및 수영강 일대에 발달한다. To get the geologic information data such as rock resources, industrial ground, development planning and so on, distribution ratios of constituent rocks with geologic age and rock type were obtained in Gyeongnam, Ulsan and Busan areas by ArcGIS 9.3 program, digital geologic and geomorphic maps of 1 : 250,000 scale. Geologic ages and rock types in the Gyeongnam area can be divided into 6 and 40, respectively. Their distribution ratios of the geologic ages are decreasing in the order of Cretaceous, Precambrian, Quaternary, Jurassic, Triassic and Tertiary. They show the wide ranges of 1.35-57.36%, and the former makes the most dominant ratio. Major rock types are 24 ones, all of which occupy the ratio of 94.58% and relatively narrow ranges of 1.15-13.64% in the area. Among them, andesite and andesitic tuff shows the more or less dominant ratio, and separately develops in the northeast, mid east and south parts of the area. In the Ulsan area, geologic ages and rock types can be divided into 3 and II, respectively. Their distribution ratios of the geologic ages are decreasing in the order of Cretaceous, Quaternary and Triassic. They show the very wide range of 6.90-79.21%, and the former makes the most prevailing ratio. Major rock types are 9 ones, which totally occupy the ratio of 98.63% and more or less wide ranges of 1.50-39.01% in the area. Among them, Jindong formation shows the most dominant ratio, and widely develops in the inner and eastern part of the area. In the Busan area, geologic ages and rock types can be divided into 3 and 10, respectively. Their distribution ratios of the geologic ages are decreasing in the order of Cretaceous, Quaternary and Tertiary. They show the wide ranges of 6.73-47.02%, and the two former makes the most dominant ratio of 88.03%. Major rock types are 6 ones, all of which occupy the ratio of 93.02% and relatively wide ranges of 4.07-47.02% in the area. Among them, alluvium forms the most dominant ratio, which mostly develops in the lower Nagdong River, West Nagdong River and Suyeong River.

Alteration zonation in the Loma Blanca kaolin deposit, Los Menucos, Province of Rio Negro, Argentina

AbstractThe Loma Blanca mine is in one of the northwest kaolinized zones of the Los Menucos area (Patagonia, Argentina). The parent rocks are andesites and andesitic tuffs from the Vera Formation, Los Menucos Group (Lower Triassic). Hayase & Maiza (1974) proposed a concentric zonation model. From the parent rock outward, four different alteration patterns were recognized: Zone 1, with sericite, chlorite and montmorillonite; Zone 2, with kaolinite and dickite; Zone 3, with dickite, pyrophyllite and alunite; and Zone 4, with quartz, disseminated sulphides and diaspore.The relationship between the chemical composition of major, minor and trace elements and the mineralogical alteration zonation was evaluated to confirm the genesis of the deposit. Fe2O3, CaO, Na2O and K2O contents decrease from Zone 1 to Zone 3, whereas Al2O3 and LOI increase in the kaolinite-alunite zone. In the chemical composition of alunite, Na > K. Large Ba, Sr, V and Zr contents were observed mainly in Zones 2 and 3. Co, Ni, Cu, Zn and Rb are more common in Zone 1. LREE are more abundant than HREE in Zones 2 and 3. In kaolinites, δ18O values range from 10.8% to 13.2%, and δD from –83% to –85%.The mineral assemblage (dickite-alunite-pyrophyllite-diaspore), the alteration zonation pattern (laterally concentric), the geochemistry of trace elements, the relation between LREE and HREE and the small δ18O values suggest that the Loma Blanca deposit was formed by hydrothermal processes.