Quartz porphyry

H.S.S. High sulfidation system L.S.S. Low sulfidation system Q.P. Quartz porphyry... 

QUARTZ PORPHYRY. One of the hypabyssal or effusive rocks chemically related to the granite or alkali family but rich in silica, which occurs as quartz phenocrysts in a crypto or microcrystalline ground mass. 

The Shackleton Limestone of the Churchill Mountains south of the Byrd Glacier is tightly folded and was intruded by ... small plutons of hornblende granite, pyroxene-hornblende diorite or gabbro, and dikes of quartz porphyry, all probably related to the Hope Granite (Grindley and Laird 1969). Faure and Felder (1984) described and sampled a complex pegmatite that intruded the Shackleton Limestone on one of two... 

Quartz-porphyry metarhyolite, Cressey Peak, Harold Byrd Mountains 519 4 31 53... 

Quartz is a widely distributed mineral species consisting of silicon dioxide (silica, SiOj) (Table 7.6). It is one of the most common minerals and is found in many varieties with very diverse modes of occurrence. Quartz is a primary constituent of rocks such as granite, quartz, porphyry, and rhyolite. It is also a common constituent in many gneisses (laminate rocks) and crystalline schists (foliated rocks). It is also, in a sense, mobile since by the weathering of silicates, silica passes into solution and is redeposited in cavities, crevices, and along joints of rocks of all types. Thus, it is not... 

Acidic rocks occurring in dykes or sills are often porphyritic, quartz porphyry being the commonest example. Quartz porphyry is similar in composition to rhyolite. 

The geology in the project area mostly comprises black to dark grey shale inter-bedded with sandstone and conglomerate of the Cretaceous Saniri Formation (Kim and Hwang 1986). This sedimentary sequence has been intruded by thin to very thick, near-vertical dykes and sills of quartz porphyry. The slope section under consideration is shown in Figure 1(a). 

For shear strength of quartz porphyry, intact samples of quartz porphyry were tested in triaxial compression following the suggested method of ISRM... 

Figure 1. View of studied slope showing the distribution of sedimentary rock (darker) and quartz porphyry (paler color). The mold from a planar failure can be seen at the right-upper part. Discontinuity orientation data are presented stereographically as follows (a) all, (b) shale, (c) quartz porphyry and (d) contact boundaries.

Section A-A is a section with simple geology there is only one relatively small intrusion of quartz porphyry exposed in the cut slope and it was therefore assumed (conservatively) that failure could occur at this section as a translational failure along fully-persistent bedding-parallel discontinuities. Cd-culated Factor of Safety (F ) is about 1.3 for dry... 

Figure 2. Kinematic stability analysis by stereographic projection (a) for all discontinuities in the cut-slope, (b) only bedding planes in shale, (c) only joints in quartz porphyry and (d) only contact boundaries of shale and quartz porphyry.

Section B-B is intruded by many quartz porphyry dykes and for this section the slope needs to be considered and analysed in much more detail regarding the potential failure geometries. The irregularly developed vertical joints in shale and contacts between shale and quartz porphyry were assumed for analysis to provide vertical release surfaces where cleft water pressure could develop. Figure 3 illustrates how each potential failure mode was analysed in turn both for dry conditions and with an assumed water table at the ground surface. 

Table 1. Factors of safety for potential failure modes in the shale cut-slope with major intrusions of quartz porphyry at the section B-B of Figure la as shown in Figure 3. 

The volcanic activity was followed by pneumatolytic and hydrothermal processes. Mineralization occurs in tuffites, quartz porphyries and arkosic shales and is represented by pitchblende, molybdenite, chalcopyrite, tetrahedrite, galena, sphalerite, arsenopyrite, magnetite, ilmenite, hematite and supergene minerals. Surprisingly, according to Ruzicka, there is no host-rock alteration. 

Ammonia tanks, Pahute Mesa K-feldspar, quartz porphyry at Rock House 19.38 15.75 39.28 Doe (1968) ... 

---