Abstract--Li-bearing smectite minerals occurring as hydrothermal alteration products of magnesium silicate minerals in skarns associated with the Moldova NouL Romania, porphyry copper deposit were examined by X-ray powder diffraction, infrared spectroscopy, and thermal and chemical analyses. Libearing smectite containing 0.45-0.50 Li/unit cell is common, whereas smectite containing 0.21-0.33 Li/ unit cell is less common. Both materials coexist with talc and kerolite. The Li-bearing smectite minerals (b = 9.111 A) contains semi-ordered or ordered stacking and is highly crystalline, similar to saponite. After 3-yr storage under laboratory conditions in an air-dried state (RH = 50%) or after heating for 2 hr at 100", 200 ~ 300", or 400"C, the Li-bearing smectite minerals showed characte~ ~stics of a regular 1:1 interstratification of anhydrous and dihydrate layers. Some segregation of the anhydrous, monohydrate, and dihydrate layers was noted.The amount of Li-for-Mg substitution was found to be close to that in hectorite, and the number of octahedral vacancies was similar to that in stevensite. This Li-bearing smectite apparently formed directly from colloidal suspensions at atmospheric temperature and pressure.

The pyrophyllite occurs in several places in Romania. From a genetic point of view, these minerals formed by four geological processes : weak metamorphism, diagenesis, hydrometasomatism and hydrothermalism. There can be distinguished : anchimetamorphic-hydrothermal mobilization pyrophyllites, the pyrophyllites in the lower part of the diagenesis-upper part of the anchizone, the pyrophyllites in the lower part of the anchizone, the pyrophyllites in the hydrometasomatic argillization zones and the hydrothermal pyrophyllitic clays. The diagenetic and anchimetamorphic pyrophyllitic rocks formed by the weak metamorphosis of some Upper Carboniferous-Lower Liassic kaolins (of fire clay type). We consider the pyrophyllite as a mineral characteristic of the anchizone. 6 crystallinity indices (5 X-ray and 1 IR) are proposed for estimating the crystallinity degree of the pyrophyllites ; the new ones (3-6) point out better the existing differentiations. The geology, petrography, mineralogy and chemistry of the pyrophyllitic rocks in Romania, as well as the pyrophyllite-kaolin minerals genetic relation are presented. The pyrophyllite-nacrite paragenesis is characteristic of the anchizone, while the pyrophyllite-dickite paragenesis is characteristic of the hydrothermalism.

SAPONITE FROM MOLDOVA NOUA, ROMANIA Argilization associated with hydrothermal activity in the vicinity of a 'porphyry copper' deposit near Moldova Noun, western Romania, is represented mainly by trioctahedral clay minerals. These include saponite, hectorite, stevensite, sepiolite, chlorite, vermiculite, kerolite, talc, and members of the serpentine group (Ianovici & Neac~u, 1970; Neac~u, 1970). Some saponite formed by direct crystallization from hydrothermal solutions but it occurs mainly as pseudomorphous replacements of grossularite and diopside, and less commonly replacing serpentine minerals and sepiolite; it is frequently associated with calcite. Chemical analyses of two samples of saponite are given in Table I and the corresponding structural formulae are given below: sample 4206 (Si~.35Tio.olAlo.64)(Mgs.44Alo.27Fe3+o.2oMno.ol)O2o(OH)4(C ao.39Nao.01), nH20 sample 4261 (SiT.35Tio.03Alo.62) (Mgs.~2Alo.loFe3+o. 12Mno.ot)O20(OH)4 (Ca0.31Nao.02Ko.o~). rt H20 Cation exchange capacities, determined by NH4-exchange, and constituents of the original exchangeable cation assemblage are shown in Table 2. Calcium is the dominant exchangeable cation in the natural clays. The saponites from Moldova No~a show both lower Al-for-Si substitution in the tetrahedral sheet and lower Al/Fe-for-Mg substitution in the octahedral sheet than most saponites described in the literature. However, the octahedral cation totals of 5.85 and 5.95 are normal for trioctahedral smectites and the interlayer cation charges of 0.39 and 0.40 are are normal for saponites. Under the microscope the saponite occurs as colourless crystals 0.001-0.14 mm (average 0-01 mm) in size. Refractive indices and birefringence have the following values: n v-n~ = 1.500-1.485 = 0.015. The DTA curve shows an endotherm at 150~ resulting from loss of interlayer water,. followed by a smaller endotherm at 260~ due to loss of hydration water of the Ca 2 § cation (Mackenzie, 1957). No further reactions are noted on DTA, DTG and TG curves until ~840~ At this temperature structural water is lost, in common with saponites from other localities (Mackenzie, 1957; Todor, 1972). XRD patterns are shown in Fig. 1. Small peaks at 3.03 and 3.34 A are due to the presence of calcite and quartz impurities. The main difference between XRD traces of saponites from Moldova Nou~i is in the position of the d(060) reflection, which varies in the range 1.525-1.533 A. This variation is due mainly to Al-for-Si substitution in the tetrahedral sheet and, to a lesser extent, to substitutions within the octahedral sheet.