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Retrograde Metamorphism of the Lower Devonian Littleton Formation in the New Salem Area, West -Central Massachusetts

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Retrograde Metamorphism of the Lower Devonian Littleton Formation in the New Salem Area, West -Central Massachusetts RETROGRADE METAMORPHISM OF THE LOWER DEVONIAN LITTLETON FORMATION IN THE NEW SALEM AREA, WEST -CENTRAL MASSACHUSETTS BY KURT T. HOLLOCHER I mm 1--------1 Sample NS 71 Retrograded Garnet CONTRIBUTION NO. 3 7 DEPARTMENT OF GEOLOGY 8 GEOGRAPHY UNIVERSITY OF MASSACHUSETTS AMHERS~ MASSACHUSETTS RETROGRADE 1'1ETAMORPHISM OF THE LOWER DEVONIAN LITTLETON FORMATION IN THE NEVI SALEM AREA, WEST-CENTRAL MASSACHUSETTS by Kurt T. Hollocher Contribution No. 37 Department of Geology and Geography University of Massachusetts Amherst, Massachusetts April, 1981 iii TABLE OF CONTENTS ABSTRACT •..•.•..•••••••••.•••••.•••.•••.••.•.•••••••••••••....•....•• 1 INTRODUCTION. • . • . • . • • . • • . • • • • . • • . • • • • . • . • • • • • . • • • • • . • . 3 Location •.••••••.••••.•.•••.•..•.•••••••••.•••••••.••.•.•.•....•• 3 Geography and Quaternary Cover ..•••.••.•.•.•.......•.•.••..••••. 3 Regional Setting and Stratigraphy •.•.••••••••.•.••••..•••.•.••.. 5 Introduction ...••.•..••.•.••.••..••.••.•••........•........ 5 Stratigraphy... • . • • . • . • . • . • . • . • • . • • • • • • . • . • . 8 Deformation and metamorphism •••..••..•.•••••• ·. • • • . • • . 10 Previous Work. • • . • • • • • • • • • • • • • . • • • • • • • • • • • • • • • . • • • • • . • . • . • . 12 Purpose of Study .••••.•••••.•••••••••••••••.••.••.••.•......... 13 Methods of Investigation •••••••••••.••.•.••..........•.•......• 14 General methods. • • • . • • • • . • • • • • • • • • • • . • • • . • • • . • • . 14 Polished thin sections •.••••••••••••••••••••.•.•••.••...•. 14 Electron microprobe analysis •.•.•••..•.••.•...••......•... 16 Acknowledgements. • • • . • • • • • . • . • . • • • • • • • • • • • • • • . • • . • • • • • • . • • 17 DESCRIPTION OF ROCKS. • . • • • • • • • • • • • • • . • • • • • • • • • • • . • • . • . • • • • . • . • . • . 17 Part ridge Formation. • • • • • • • • • • . • • • • • • • • • • • • • . • • . • • • • • • • • • • . • • 17 Clough Quartzite •••••••••••••••••••.•••••••••••••.•••..••••..•• 18 Fitch Formation. • • • • • . • • • • • • • • • • • • • • • • • • • • • • • • . • • • . • • • • • • • • • • • • 18 Littleton Formation •••••••••••.••••••••••••.•.•.•••••.••...•.•• 18 Distribution of Metamorphic Zones ••.•.••••••••••..•••••••..•.•• 20 Description of Analyzed Samples ••••••••••••••..•••••••••.•••••• 23 UOlA .•.•••••••.••••.•••.•.•••••••••••.••••.••••••.••••.••• 23 NS118 ••••••••••••••••••••••••••••••.•••••.•••••••.•••••.•• 26 iv NS18. • . • . • . 26 NS87 .......................•.............................. 26 NS85....... • . • . 27 NS90 ....................•...•...............•............. 27 NS71 ....................•..•........•..................... 27 MINERALOGY AND CRYSTAL CHEMISTRY .•.................................. 28 Introduction ..................•................................ 28 Analyses ....................................................... 29 Sillimanite ............•.......................••.............. 30 Field occurrence. 30 Textures in thin section .................................. 32 Staurolite. • . 34 Field distribution and habit .........•.•.................. 34 Appearance in thin section ................................ 35 Structural formula and crystal chemistry .................. 39 Structural formula recipe ...•...•......................... 41 Chemical analyses. • . 42 Garnet .................•...............•.•....................• 45 Field distribution and habit ..•...•.....................•. 45 Textures in thin section ...........•....•.•...•.......... 46 Chemical zoning. • . • . • . 48 Rim compositions. • • . • . • . • • . • . 57 Discussion of garnet stoichiometry ........................ 62 Biotite .......... ,• ............•.........•.•..•................. 63 Field distribution and appearance ..•••.....•.•..........•. 63 v Appearance in thin section .•..•..•....•................... 64 Chemistry... • . • • . 66 Muscovite .•..................•..•..•..•......•...•............• 80 Field habit. • . • • . • . • . • . • • . • . 80 Appearance in thin section •......•...••..••............... 80 Chemistry. • . • . • • . • . • . 82 Chlorite. • . • • . • . • • • • . • . • . 100 Field appearance ..•.•.•..........•...•......•..•......... 100 Optical properties ........•.•••.......•...••............. 101 Appearance in thin section •......•••...•.•...........•... 102 Chemistry •........•...•..•...........••.................. 103 Chloritoid ....•....•...•..•.......•.•••...••.........•.•...... 117 Field occurrence •.••.••.••.....•.•...•..••....•..••..•... 117 Appearance in thin section •.••.•••..•.•.....••.....•..•.. 117 Chemistry. • . • . • . • . • . • • . • . • . • • . • . 119 Plagioclase ..•.........•.•.•••..••..•....•.••.•.••••......•... 119 Field appearance. • • . • . • • • • • . • • . • • . • . • • • . • . • . 119 Appearance in thin section ..•.•.•.....•.....•••.•..••.... 121 Chemistry. 12 2 K-feldspar. 125 Occurrence. 125 Chemistry ................................................ 126 Ilmenite. 129 Occurrence and habit •....••••..•.••••••.••••••••••.••.••• 129 Chemistry ................................................ 130 vi Anatase ......•.................•.....................•........ 138 Occurrence and h~it ........ o•••o••o••o•o•••·••••o······· 138 Chemistry. • . • . • . 141 Stability .......•................•..................... o. 141 Sphene .........•......................... o •••••••••••••••••••• 144 Occurrence ... o •••••••••••••••••• o •••••••••••••••••••••••• 144 Chemistry .......................... o •••••••••••••• o •••••• 145 Rutile ... o •••••••••••••••••••• o ••••••••••••••••••••••••••••••• 151 Apatite ....................... o. o •••••••••••• o •••••••• o 0 •••••• 152 Tourmaline ............ o o o •• o ••• o •••••••••••• o • • • • • • • • • • • • • • • • • 154 Zircon .................•..... o •• o ••••••••••••••••• o o •••••••••• 155 Graphite .....•.............. o ••••••••••••••••••••••••••••••••• 155 Allanite. o ••• o •••••••••••••••••••••••••••••••••••••••••••••••• 156 Pyrite ........... o •••••••••••••••••••••••••••••••••••••••••••• 157 Quartz ..........................•............................. 158 Weathering Products ....•....•.......•......................... 158 Cathode Luminescence......... • . 159 PHASE RELATIONS. • . • . • . • . • . 160 Introduction •.................•...........................•... 160 Feldspars. • . • . • . • . • • . 160 Micas .....................•.........•...........•......•.....• 162 Alkali-Alumina System .•..... 0 ••••••••••••••••••••••••••••••••• 166 Ti0 -FeO-H 0 System ....••.•...•....•........•.......•......... 168 2 2 AKFM Tetrahedron ......•.......•.......•.•........•...........• 170 Muscovite Projection ....••...............••...•••.•........... 172 vii RETROGRADE REACTIONS. 17 4 Introduction ..................•............................... 174 Sillimanite-Out Reaction .......................•.......•...... 176 Staurolite-Out Reaction ....................................... 180 K-feldspar-In Reaction ........•...•........................... 183 Garnet-Out Reactions ................•......................... 187 Introduction .•.............•............................. 187 Garnet rim, biotite present reaction ..................... 189 Garnet core, biotite present reaction .................... 191 Garnet core, biotite absent reaction .•................... 191 Biotite-Out Reactions .•.•..................................... 194 Chloritoid-In Reactions ....................................... 197 Introduction .•....................•...................... 197 Garnet-chlorite continuous reaction ....•......•..•....... 198 Phengitic muscovite continuous reaction .................. 200 Manganese stabilization of chloritoid .•.......•.......... 201 Ilmenite-Out, Anatase-In Reaction .........................•... 205 Sulfide-Silicate Reactions ...•.........•.•........•........... 207 Summary of Retrograde Reactions... • • . • . • . 210 Mobility of Chemical Components ....•......... o •••••••••••••••• 212 CONDITIONS OF METAMORPHISM. • • . • • • . • . • . 215 Introduction •...•.•..•....•.••............•.. o •••••••••••••••• 215 Published Data on Univariant Reactions ....•.......••.......... 216 Introduction ••....•......•...•..•..•.•...•••.•........... 216 Explanation of reactions ...•.•.••.•..••..•.••.. o o o o o. o • • • 217 viii Probable field of prograde metamorphism ..•............... 220 Probable field of retrograde metamorphism ........•.....•. 222 Coexisting Mineral P-T Estimates .•.•...•..•................... 222 Garnet-biotite thermometers ...........•.................• 222 Muscovite-paragonite solvus .............................. 224 White mica-alkali feldspar solvi. ........•............... 226 Muscovite celadonite component ........................... 226 Alkali feldspar sol vus. • . 228 Cordierite equilibria ...................•...............• 229 Garnet-plagioclase calcium partitioning .........•........ 230 Biotite-muscovite titanium partitioning .................. 231 Independent Constraints for Metamorphic Conditions ....•....... 232 Prograde metamorphism .................................... 232 Retrograde metamorphism ......•..•••............•........• 233 Discussion of Prograde P and T ................................ 236 Discussion of Retrograde P and T ....•.••...•.................. 237 METAMORPHIC FLUID COMPOSITION ...........................•.....•...• 238 TIMING OF RETROGRADE METAMORPHISM .................•................ 242 WATER FOR RETROGRADE HYDRATION REACTIONS ..............•.....••..... 243 Quantity .......•.........•..........•..•....•....•........•..
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