Bedrock Geology and Asbestos Deposits of the Upper Missisquoi Valley and Vicinity, Vermont GEOLOGICAL SURVEY BULLETIN 1122-B Bedrock Geology and Asbestos Deposits of the Upper Missisquoi Valley and Vicinity, Vermont By W. M. CADY, A. L. ALBEE, and A. H. CHIDESTER CONTRIBUTIONS TO ECONOMIC GEOLOGY GEOLOGICAL SURVEY BULLETIN 1122-B Survey of an area in which 80 percent of the asbestos produced in the United States has been mined NITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1963 UNITED STATES DEPARTMENT OF THE INTERIOR STEWART L. UDALL, Secretary GEOLOGICAL SURVEY Thomas B. Nolan, Director For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C., 20402 CONTENTS Page Abstract. _________________________________________________________ B 1 Introduction._____________________________________________________ 2 Geography. ___________________________________________________ 3 Previous work.________________________________________________ 4 Present investigation_________________________________________ 5 Acknowledgments _____________________________________________ 5 Geology---_----_-_--------_-----___--_____.______________________ 6 General statement._--_-_------___-_-__________________________ 6 Regional age correlations_______________________________________ 7 Metamorphosed sedimentary and volcanic rocks __________________ 8 Hazens Notch formation___________________________________ 11 Schist, gneiss, and quartzite_____________________________ 11 Amphibolite __________________________________________ 13 Jay Peak formation________________________________________ 13 Belvidere Mountain amphibolite_____________________________ 15 Ottauquechee formation.___________________________________ 18 Carbonaceous phyllite_-_-_-_-______-__________--_______ 19 Carbonaceous quartzite________________________________ 19 Quartz-sericite-chlorite phyllite._________________________ 20 Phyllitic graywacke____________________________________ 21 Stowe formation___________________________________________ 22 Sericite-quartz-chlorite-albite schist and phyllite,_________ 23 Carbonaceous quartz-sericite-chlorite schist and phyllite____ 23 Greenstone ___________________________________________ 24 Phyllitic graywacke____________________________________ 25 Umbrella Hill formation____________________________________ 25 Moretown formation_______________________________________ 27 Quartz-sericite-albite-chlorite granulite___________________ 28 Quartz-sericite-chlorite phyllite-slate_____________________ 29 Sericitic and chloritic quartzite__________________________ 30 Coburn Hill volcanic member.__________________________ 30 Shaw Mountain formation._________________________________ 32 Quartz conglomerate.__________________________________ 32 Mica phyllite._______________________________ 32 Crystalline limestone.__________________________________ 33 Northfield slate_________________________________________ 33 Intrusive igneous rocks and associated alteration products._________ 34 Ultramafic and associated rocks____________________________ 35 Distribution __________________________________________ 35 Lithologic description__________________________________ 36 Dunite___ ______________________.____________ 36 Peridotite_ _____________________________________ 38 Serpentinite_ _ _____________________________________ 39 Calc-silicate rock___________________-_--__-_--____- 41 in 17 CONTENTS Geology Continued Intrusive igneous rocks and associated alteration products Continued Ultramafic and associated rocks Continued Lithologic description Continued Pag» Antigorite-chlorite rock___________-_-_-_-____-____ B-42 Talc-carbonate rock----_-________-_-_-_-________-__ 42 Carbonate rock._____________-_-_______-_----__--__ 43 Steatite ________-_____----___-__-_-_-_-___________ 44 Chlorite rock--___-___-_-__-_-_----------__-------- 44 Genetic relationships--_________________________________ 45 Metagabbro _______-___-_-_-_-________-_-_---_-__-------_- 47 Eltey Mountain granite_____-________-_-_-_-______--___---- 50 Lamprophyre_ _ __ _ _______-_-_--______-__-_-_-_-__-_-_____- 53 Metamorphism_ _ ________________________________________________ 54 Structure.-_ ______________________________________________________ 56 Major structural features.----------.---------------------------- 56 Minor structural features.______________________________________ 57 Bedding and bedding foliation_---_-_-_-----------------~---_ 58 Layering in ultramafic rocks ________________________________ 59 Folds and crinkles_____________-_____---_-______-_---_-_-__ 59 Slip cleavage and transverse schistosity; fracture cleavage; fold layers __________________________________________________ 61 Other minor structures.____________________________________ 62 Structural synthesis__________________________________________ 63 Asbestos deposits __________________________________________________ 67 History and development_-_______----_--_-_--_--_----_-__------ 67 Geologic relationships-___-______--_-__----____-_-_-_-_---__---_ 68 Dispersed fiber._______________--_-_-_-_-_-_-__--_---__-_-_ 69 Slip-and cross-fiber veins.________-_________--_-_-_-___-____ 70 Other mineral resources________________-_-______-_-_-_-_----_______ 70 Talc._____--_.____-__-__________-_---_-_-_-_-----_---------__ 70 Iron __-_----__-_____-________---____-___-_-_-___-----__-__-__ 71 Chromite__-____-__-___________-__-__-_-___-_-----_--_-__-__ 71 Copper____-___-_-________-____---_-_--__ ________________ 72 References cited______-______________-__---_---_---_--_-------__-_- 72 Index-_______________________._____________________________ 75 ILLUSTRATIONS Page PLATE 1. Geologic map and structure sections of the upper Missisquoi Valley and vicinity, Vermont-______ ______ __________In pocket FiGtJEE 1. Index map showing location of the upper Missisquoi Valley and vicinity, Vermont-.______________________________ B 3 2. Diagrammatic sections illustrating the two principal types of zonal relations at the contacts of ultramafic plutons_ _______ 37 3. Large-scale diagram illustrating the relation between minor cross folds and minor folds of the longitudinal fold system. _ 60 4. Block diagram illustrating fold layers in interbedded granu- lite and quartzite- of the Moretown formation__________ 62 CONTENTS TABLES Page TABLE 1. Correlation of the rock formations of north-central Vermont and adjacent Quebec______---____----_-__-----_---In pocket 2. Estimated modes of selected metamorphosed sedimentary rocks _______________________________________________ B 9 3. Estimated modes of selected metamorphosed volcanic rocks__ 10 4. Estimated and measured modes of the intrusive igneous rocks. 34 CONTRIBUTIONS TO ECONOMIC GEOLOGY BEDROCK GEOLOGY AND ASBESTOS DEPOSITS OF THE UPPER MISSISQUOI VALLEY AND VICINITY, VERMONT By W. M. CADY, A. L. ALBEE, and A. H. CHIDESTER ABSTRACT The upper Missisquoi Valley and vicinity as described in this report covers an area of about 250 square miles at the headwaters of the Missisquoi River in north- central Vermont. About 90 percent of the area is forested and the remainder is chiefly farm land. The topography reflects the geologic structure and varied resistance of the bed­ rock to erosion. Most of the area is on the east limb of the Green Mountain anticlinorium, which is the principal structural feature of Vermont. The bedrock is predominantly sedimentary and volcanic rock that has been regionally metamor­ phosed. It was intruded before metamorphism by mafic and ultramafic igneous rocks, and after metamorphism by felsic and mafic igneous rocks. The metamor­ phosed sedimentary and volcanic rocks range in age from Cambrian(?) to Middle Silurian, the intrusive igneous rocks from probably Late Ordovician to probably late Permian. Metamorphism and principal folding in the region occurred in Middle Devonian time. The metamorphosed sedimentary and volcanic rocks make up a section at least 25,000 feet thick and can be divided into nine formations. The Hazens Notch formation of Cambrian (?) and Early Cambrian age is characterized by carbona­ ceous schist. It is succeeded in western parts of the area by the Jay Peak forma­ tion of Early Cambrian age, which is chiefly a schist that is distinguished by the general absence of carbonaceous zones; in central parts of the area the Hazens Notch formation is followed by the Belvidere Mountain amphibolite, probably the youngest of the formations of Early Cambrian age. The Ottauquechee formation, composed of carbonaceous phyllite and quartzite, and phyllitic graywacke, is of Middle Cambrian age. The Stowe formation of Late Cambrian(?) and Early(?) Ordovician age overlies the Ottauquechee and is predominantly noncarbonaceous schist, though it also contains greenstone and carbonaceous schist and phyllite. The Umbrella Hill formation of Middle Ordovician age is characteristically a conglomerate in which the mineral chloritoid is common. The overlying More- town formation, also of Middle Ordovician age, contains granulite and slate, also greenstone and amphibolite of the Coburn Hill volcanic member. The Shaw Mountain formation, made up of conglomerate, phyllite, and limestone, is the oldest Silurian unit. The Shaw Mountain formation is succeeded by the North- field slate of Middle Silurian age. The igneous rocks of the region include various ultramafic plutonic rocks, such as dunite, peridotite, and serpentinite, probably of Late Ordovician age; sills and nearly concordant dikes of metagabbro of Late Ordovician age; biotite granite B-l B-2 CONTRIBUTIONS TO ECONOMIC GEOLOGY