. Elements of geology. Geology. 118 LYELL'S ELEMENTS OF GEOLOGY. Plutonic Rocks. CHAPTER IX. PLUTONIC ROCKS GRANITE. General aspect of graniteâDecomposing into spherical massesâRude colum- nar structure â Analogy and difference of volcanic and plutonic formationsâ Minerals in granite, and their arrangementâGraphic and porphyritic graniteâ Occasional mineralsâSyeniteâSyenitic, talcose, and schorly granitesâEuriteâ Passage of granite into trapâExamples near Christiania and in Aberdeenshireââ Analogy in composition of trachyte and granite â Granite veins in Glen Tilt, Cornwall, the Valorsine, and
. Elements of geology. Geology. 118 LYELL'S ELEMENTS OF GEOLOGY. Plutonic Rocks. CHAPTER IX. PLUTONIC ROCKS GRANITE. General aspect of graniteâDecomposing into spherical massesâRude colum- nar structure â Analogy and difference of volcanic and plutonic formationsâ Minerals in granite, and their arrangementâGraphic and porphyritic graniteâ Occasional mineralsâSyeniteâSyenitic, talcose, and schorly granitesâEuriteâ Passage of granite into trapâExamples near Christiania and in Aberdeenshireââ Analogy in composition of trachyte and granite â Granite veins in Glen Tilt, Cornwall, the Valorsine, and other countries â Different composition of veins from main body of graniteâMetalliferous veins in strata near their junction with graniteâApparent isolation of nodules of graniteâQuartz veinsâWhether plu- tonic rocks are ever overlyingâTheir exposure at the surface due to denuda- tion. The plutonic rocks may be treated of next in order, as they are most nearly allied to the volcanic class, already considered. I have described, in the first chapter, these plutonic rocks as the unstratified division of the crystalline or hypogcne formations, and have endeavoured to point out in the Frontispiece, at D, the position which they occupy, when first formed, relatively to the volcanic formations, B. By some writers all the rocks now under consideration have been comprehended under the name of granite, which is, then, understood to embrace a large family of crystalline and com- Fig. Mass of granite near the Sharp Tor, Cornwall. pound rocks, usually found underlying all other formations; whereas we have seen that trap very commonly overlies strata of different ages. Granite often preserves a very uniform char- acter throughout a wide range of territory, forming hills of a pe-. 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 perfec
Size: 2768px × 903px
Photo credit: © Paul Fearn / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorlyellcharlessir17, bookcentury1800, booksubjectgeology
