Geology and Mineral Resources of Paraguay A Reconnaissance

24 GEOLOGY AND MINERAL RESOURCES OF PARAGUAYFIGURE 17. Black porphyry (specimen P-32) from dike parallel to the Del Puerto vein near Caapucu shows andesinic phenocrysts, /, in finely crystallinematrix, a rather coarsely crystalline cognate xenolitli, c-x, not discernible in the hand specimen, and quartz (q). X 20. Crossed nicols.In the norm symbols (Washington (1917)), thefollowing significance attaches to the four parts ofthe symbol.The initial Roman numerals termed the "class" indicatesthe relation of salic to femic minerals, that is,TABLE 2. Spectrographic analyses of Precambrian rocks ofParaguay[Analyst: Paul R. Barnett, TJ. S. Geological Survey. Tr.=trace; concentrationuncertain. Looked for but not found, As, B, Bi, Cd, Ge, In, Pt, Sb, Ta, Th, Tl,U, and W]Ag_____Ba_ _Be..___Co._.__Cr_____Cu____.Ga_ _La...__Mo_.__Nb__._Ni._ -.Pb_.___Sc_-._Sn__Sr . ._V......Y.____.Yb____.Zn_____Zr ...P-310. 0001.1.0006.0002.0003.003.002.006.0002.0010 .009.00050.02.002.005.0004.2.02P-34 P-58b P-59 P-600 0 0 0 .05 .1 .07 .2.0007 .0004 .0003 0. 0002i Tr. Tr. .0008. 0004 . 0002 .0001 .0003.0007 .0003 .0002 .0007.002 .002 .001 .001.006 .006 .006 0.0002 .0001 .0003 .0003.001 .001 .001 .0020 . 0004 0 0 .002 .004 .003 .004.001 .0003 .0003 .0010 0 0 0.02 .009 .009 .05.0009 .002 .0004 .004.007 .006 .005 .007.0007 .0004 .0004 .00030 0 0 .03 .01 .040 .01P-62P-75 P-lOla P-lOlb0 0. 00004 0 .004 .02 .1.0007 .0006 .00050 .0005 .0005Tr. .002 .001.0002 .002 .001.003 .004 .00100 00 .002 .0002.003 .01 00 .001 .0008.005 .002 .0030 0 .00040 .0006 0 .0006 .002 .01Tr. .007 .005.007 .02 .004.0008 .002 .00040 0 0 0.01 .03 .08 .01P-740 0 .07 .0020 .0004.0003 0.0001 .0001.0003 .0002.001 .002.005 0.0002 .0003.001 .0020 0 .003 .003.0004 00 0.03 .002.002 Tr..004 .004.0002 .00040 .02NOTE. See following table for description of specimen and locality of collectionnumbers.Field No.P-31 .....P-34___P-58b..._-P-59 __ _P-60__P-62_____.P-74 _____P-75- -P-lOlb. _.RockPorphyry, dark phase ...Rhyolite agglomerate. _ _Rhyolite porphyry ......Porphyry (fine grained) _LocalityCountry rock of Del Puerto vein outcropnear Caapucu.Highway quarry near Ypacarai.Acahay caldera.North of Caapucu on Quiindy road.Near Caapucu.quartz-|-f el dspars+feldspathoids versus ferromagnesiansilicates-)-oxides + carbonates-]-phosphates, and others.There are five classes.The second numeral indicates the order, based ondifferences in the chief subgroup of the preponderantsalic or femic group, and serves to distinguish thosechemical characters that are dependent on the dominantacid-forming components of the magma, silicon, titanium,and ferric iron. For rocks not definitely femicin character, there are nine orders.The third numeral indicates the rang, based on theproportions of alkalies to lime in the preponderant salicage.age.