Marginal zone

Certain species of Pertusaria, Lecanora, Ochrolechia, etc., have concentrically zoned margins. The zones arise because rapid summer growth is whitish and the narrow dormant zone in winter is darker. Each zone is therefore 1 year s growth and the width is an accurate measure of radial growth... 

The side depth of the thickener is determined as the sum of the depths needea for the compression zone and for the clear zone. Normally, 1.5 to 2 m of clear liquid depth above the expected pulp level in a thickener will be sufficient for stable, effective operation. When the location of the pulp level cannot be predicted in advance or it is expected to be relatively low, a thickener sidewall depth of 2 to 3 m is usually safe. Greater depth may be used in order to provide better clarity, although in most thickener applications the improvement obtained by this means will be marginal. 

Protection with internal fuses is easier, as fuses are provided for each element which can contain the severity of the fault well within the safe zone in all probability. Some users even recommend capacitor units 250/300 kVAr and above with internal fuses only. Figure 26.1 shows a typical operating band of (he internal fuses for an internally protected unit. It demonstrates a sufficient margin between the operation of (he fuses and (he shell s safe zone. The fuse characteristics are almost the same for all manufacturers. 

The thertnal model consists of two zones (Fig. 11,54). The hall is modeled w ith an air node for the occupied zone and another air node for the rest of the hall. The main heat source in the hall is the insnlatiou through the glazed roof. Additional internal hear sources are rather marginal and therefore are nor considered in the simuiation. 

The draft risk due to cold air pillows under the roof glazing dropping into the occupied zone was determined by transient CFD calculations. As can be seen from Fig. 11.57, velocities do not exceed 0.2 m/s. Therefore, the draft risk was assumed to be marginal. 

Choosing the second option, we would increase the flowrates in zones I and decrease the flowrate in zone IV. Then adjust the flowrates in zones II and III (the feed flowrate is slightly decreased to improve the margin in these two zones). With the assistance of the simulation program, we can determine to what degree the flowrates should be decreased or increased to obtain the target purity. 

For example. Date et al. (1983) recognized the following alteration zones in the Fukazawa Kuroko mine area of Hokuroku district from the centre (near the orebody) to the margin (1) sericite-chlorite zone (zone 111 in Figs. 1.20-1.22) characterized by quartz + sericite Mg-rich chlorite (2) montmorillonite zone (zone 11 in Fig. 1.20) characterized by Mg-Ca-type montmorillonite + quartz kaolinite calcite sericite Fe-rich chlorite and (3) zeolite zone (zone 1 in Fig. 1.20) characterized by clinoptilolite + mordenite + Mg-Na-type montmorillonite cristobalite calcite or analcime + Mg-Na-type montmorillonite + quartz calcite sericite Fe-rich chlorite (Fig. 1.20). 

Figure 1.80. Zonal sequence of the advanced argillic alteration from the central to marginal zone in section of A -B in Fig. 1.79 and from upper horizon to lower horizon (Shikazono, 1985a)...

Shikazono (1985a) has studied hydrothermal alterations in the epithermal Au-Ag mine district in Izu Penin.sula, middle part of Honshu, and indicated that (1) the propylitic alteration occurs widely in the district (2) at the centre of the district and stratigraphically upper horizon, there exists advanced argillic alteration (3) epithermal Au-Ag vein-type deposits are distributed at marginal zone in the district (Fig. 1.125) ... 

Izawa et al. (1990) recognized the following alteration zones from the vein towards margin of the Hishikari Au-Ag mine area, chlorite-sericite zone (zone IV), interstratified clay mineral zone (zone III), quartz-smectite zone (zone II) and cristobalite-smectite zone (zone I) and least altered zone (L.A. (least altered) zone) (Fig. 1.131). 

Figure 1.147. Jackson s curve and arc stress reorientations. Apparent swing motion of Pacific Plate (Jackson et al., 1975) and regional stress orientation at the Northeast Honshu convergent margin are illustrated in order to show their synchronous relationship. Dashed line represents the average trend of the Hawaiian volcanic chain. Pacific plate moves along the direction with fluctuation in reference to Hawaii Hot Spot. Vertically shaded parts of the graph indicate the climax phases of clockwise episodes . Lower part of the figure shows the phases and reversals in orientation of tectonic stress fields on the inner zone of Northeast Honshu Arc (Takeuchi, 1987).

The vein-type deposits can be divided into two based on the metals produced precious (Au, Ag) and base metal (Pb, Zn, Ag, Mn, Cu, Fe) vein-types. There are two sub-types of the base metal vein-type deposits, the Cu-Pb-Zn sub-type and the Pb- Zn-Mn-Ag sub-type. Cu-Pb-Zn veins occur in southern part of the province. Large Pb-Zn-Mn-Ag veins and Au-Ag veins are distributed in northeastern part. In the northeastern part, Au-Ag vein-type deposits occur in marginal zones of the province, while the base metal-rich deposits (Pb-Zn-Mn veins and Kuroko deposits) in central zone (Fig. 1.149). The marginal zone is characterized by exposure of Quaternary volcanic rocks and Plio-Pleistocene volcanic rocks in which Au-Ag veins occur, whereas the central zone is by thick submarine volcanic rocks (Fig. 1.150), in which base metal-rich deposits (base metal veins and Kuroko deposits) occur (Fig. 1.150). Tertiary volcanic rocks, Quaternary volcanic rocks and faults are distributed, trending generally from NW to SE. Some Cu-Pb-Zn veins in southern part are hosted by basement rocks. On the other hand, Pb-Zn-Mn-Ag and Au-Ag veins occur in Tertiary and Quaternary volcanic rocks. 

It is inferred that in the northern part of the province submarine volcanic rocks are thick in the central zone, while at marginal zone it is thin and the Plio-Pleistocene subaerial volcanic rocks are exposed. The vein-type deposits occur widely in the province. The precious vein-type deposits occur in relatively young (Plio-Pleistocene) volcanic rocks, while large base metal vein-type deposits (e.g., Toyoha, Inakuraishi, Ohe) and Kuroko deposits (e.g., Kunitomi) occur in central zone where thick Miocene submarine volcanic rocks are distributed (Figs. 1.149 and 1.150). Small base metal vein-type deposits occur in Paleozoic rocks in the southern part. 

The deposits are characterized by conspicuous metal zoning and polymetallic mineralization. From the centre to margin of the mine district, the following zonings are recognized Sn-W-Bi-Cu zone, Cu-As-Zn zone, and Zn-Pb-Cu-As zone (Nakamura, 1970). 

The deposits are characterized by conspicuous alteration zoning from the centre (orebody) to margin (Tokunaga, 1955 Doi, 1972 Urashima et al., 1981, 1987). They are siliceous zone, alunite zone, kaolinite zone, sericite zone and montmorillonite zone. 

Hydrothermal alteration in the Osorezan area is extensive. At the foot of the lava dome, highly silicified alteration occurs. From this zone towards marginal parts, kaolinite zone and montmorillonite zone exist. This type of alteration was caused by the acid hydrothermal solution. But at present such acid hot solutions are not present in the Osorezan area. The acid solution is considered to be of volcanic origin. It is therefore thought that the water chemistry evolved from extremely acid at the early stage to neutral pH at present (Aoki, 1992a). 

Sarin MM, Kim G, Church TM (1999) °Po and °Pb in the South-equatorial Atlantic distribution and disequilibrium in the upper 500 m. Deep-Sea Res II 46 907-917 Schmidt S, Andersen V, Belviso S, Marty JC (2002) Strong seasonahty in particle dynamics of northwestern Mediterranean surface waters as revealed by " Th/ U. Deep-Sea Res 149 1507-1518 Shimmield GB, Ritchie GD, Fileman TW (1995) The impact of marginal ice zone processes on the distribution of °Pb, °Po and " Th and implications for new production in the Bellinghausen Sea, Antarctica. Deep-Sea Res II 42 1313-1335... 

Splenic marginal zone B-cell lymphoma ( villous lymphocytes)... 

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