. Bulletin of the Geological Society of America. Geology. APLITES AND PEGMATITES 537 to be: (1) Granite-gneiss, (2) Kichmond-Petersburg light gray granite, and (3) the Kichmond-Fredericksburg dark blue granite. As shown in the accompanying figures, sketched from quarry openings in the field, the granite mass of each intrusion was accompanied by the formation of pegmatitic material. Some of the pegmatites intersecting the dark blue granite which represents the latest of the granite intrusions also pene- trate the light granite, and in some cases the earliest of the intrusions, granite-gneiss. T
. Bulletin of the Geological Society of America. Geology. APLITES AND PEGMATITES 537 to be: (1) Granite-gneiss, (2) Kichmond-Petersburg light gray granite, and (3) the Kichmond-Fredericksburg dark blue granite. As shown in the accompanying figures, sketched from quarry openings in the field, the granite mass of each intrusion was accompanied by the formation of pegmatitic material. Some of the pegmatites intersecting the dark blue granite which represents the latest of the granite intrusions also pene- trate the light granite, and in some cases the earliest of the intrusions, granite-gneiss. These conditions are well illustrated in figures 1 and 5, which show that the latest formed pegmatites intersecting the dark blue granite also extend into and intersect respectively the granite-gneiss and v / \ V \ \. 'C\'3/ue 'Gr4tirte\*'-} Figure 5.—Contact between Blue and Gray Granite. Netherwood quarry, west of Richmond. The same pegmatite cut- ting both granites is shown. the light gray granite; also figure 1 shows that a pegmatite which char- acterized the earliest period of intrusion, granite-gneiss, is abruptly cut off by the intrusion of the dark blue granite into the granite-gneiss. It will be observed from the figure that where the pegmatite is cut off by the dark blue granite it is equally as wide as in any other portion of the dike, traced for some distance in the exposed granite-gneiss. Moreover, those pegmatites which belong to the latest period of intrusion and which intersect the dark blue granite are found intersecting each other in such manner as to indicate earlier and later formation. Figure 6, which shows this, also shows that the oldest or intersected pegmatite is faulted. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Geological Society of America. [New York : The Society]
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectgeology, bookyear1890
