Pyroclastic sedimentary rocks

The area consists of Quaternary late Pliocene pyroclastics and sedimentary rocks. Marine mudstone and sandstone of Mesozoic-lower Tertiary Shimanto Supergroup are overlain by these rocks. Thick (more than 1,000 m) dacitic tuffs interbedded with marine sedimentary rocks of late Pliocene-early Pleistocene age occur. These rocks overlie altered andesite lava and dacitic pyroclastics of Miocene-late Pliocene (Yoshimura et al., 1988). 

In the preceding paragraphs we have mentioned some of the researches that are necessary on the chemical substances of the earth s surface. We come next to aggregates, including the igneous rocks, the pyroclastic and sedimentary rocks, the oceans and other bodies of water, and the atmosphere. 

Most commonly, zeolites are found in series of sedimentary rocks which contain pyroclastic material and are formed during the devitrification of this material. If the rocks are silica-rich, the zeolite species formed seems dependent upon the bulk composition and burial depth or temperature of formation (Hay, 1966). They are most frequently accompanied by silica in an amorphous or cryptocrystalline form (opal, chalcedony). Analcite and all other compositional intermediates up to the silica-rich clinoptilolite are found in this association. The most comifton clay mineral in such tuffs is montmorillonite. Zeolites are sometimes found with glauconite (Brown, et al . 1969) or celadonite (Hay, 1966 Iijima, 1970 Read and Eisenbacher, 1974) in pelitic layers or acidic eruptive rocks... 

These associations are noted by Hay (1966) as being found in sequences of sedimentary rocks or altered pyroclastics buried to depths greater than 3,000 meters and generally less than 10,000 meters. However, the limits are actually vague and the identifications imprecise. The relatively frequent occurrence and persistence of albite or potassium feldspar and alkali zeolite in such rocks leads one to believe that they can coexist stably in nature. This could be, however, a misleading conclusion based upon too few observations. The elimination of the silicic, alkali zeolites and the persistence of montmorillonite is known to exist in series of deeply buried rocks (Ii-jima, 1970 Moiola, 1970 Iijima and Hay, 1968). 

The main productive series of fractured volcanogenic-sedimentary rocks of -1270 m thickness was modeled as alternating beds of tuffs and interlayers of andesites, diorites, porphyrites. The lower series of -1600 m - effusive-pyroclastic rocks of the Paratoon suite of Myocene. The values of hydrogeologic parameters of the layers identified are presented in Table 1. Thermoconductivity coefficient of 2.0 W/m-°K was specified for the rocks in three upper layers, and 2.5 W/m °K in the rest ones, with heat capacity of 1750 J/kg-°K, density of rocks is 2500 kg/m ... 

Many investigators who have worked on the rocks of the Wyatt Formation (Sections 6.3.2, 6.4.1, and 7.1.2) and on the Thiel Mountains Porphyry have commented on the similarities of their chemical composition, their texture, their massive structure, their modes of emplacement, and their relation to underlying clastic sedimentary rocks (e.g., Vennum and Storey 1987a Pankhurst et al. 1988 Stump 1995). Even Ford and Sumsion (1971) pointed out that the Thiel Mountains Porphyry and the rocks of the Wyatt Formation are both of pyroclastic origin and formed during an episode of silicic volcaiuc activity on an immense scale because the volume of pyroclastic rocks in the Thiel Mountains alone seems to have exceeded 5,000 kml... 

The Sabatini Volcanic District developed between about 0.8-0.6 Ma and 40 ka over a wide area located just to the north of Rome. Volcanism was predominantly explosive and generated widespread pyroclastic deposits with only minor lava flows, which were emitted from a large number of centres including several calderas (e.g. De Rita et al. 1983, 1993). The vol-canism occurred along a zone of crosscutting NW-SE and NE-SW faults (Di Filippo 1993). The Sabatini rocks rest over the same type of sedimentary bedrocks as at Vico, as well over the acid volcanics of Tolfa-Manziana-Cerite complex of the Tuscany Province. 

Several ejected blocks are found in the Somma-Vesuvio pyroclastics. These include lavas, sedimentary carbonate rocks, skams, and mafic and ultramafic xenoliths (e.g. Joron et al. 1987). The latter have been suggested... 

Pyroclastic ejected by volcanic emption Radiolarians a protozoon having a sihca skeleton Sedimentary processes whereby rocks (minerals) are formed from materials derived from other rocks by weathering, erosion, and transportation... 

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