EVOLUTION OF THE WHITE MOUNTAIN MAGNIA SERIES RaNoor.pn W. CnapuaN, Vassar College CnenrBs R. wrr";;: , Cambri.d,ge,Mass. PART I. DATA Pnosr.BM In recent years, a number of intensive field and laboratory studies of the rocks of the White Mountain district in New Hamp- shire have been carried out. One result of these investigations is to show that there exists in this area a group of rocks with marked alkaline affinities (3)* to which the name White Mountain magma serieshas been applied (5, p.56). The various rock types of this group form a definite series,and wherever found in the area they possessthe same relative ages.Such a sequenceis of greatestim- portance to petrology and necessitatesan explanation. Accord- ingly, the writers have undertaken a study of this problem, the results of which are presented in this paper. ft is not pretended that this work is complete or that the problem has been entirely solved. Certain definite conclusions have been reached, however, and it is hoped that these may lead to a more complete under- standing of the evolution of the White Mountain magma series. The writers are especiallyindebted to ProfessorMarland Billings of Harvard University for his valuable assistancein preparing this paper. Several of the major ideas presentedhere were first sug- gested by Professor Billings, and these have led to a clearer under- standing of many of the intricate problems encountered in the course of the work. The writers also wish to thank ProfessorEsper S. Larsen, Jr., and ProfessorR. A. Daly for their many helpful suggestionsand criticisms. The new mineral analyses quoted here were made by F. A. Gonyer of Harvard University. fn the course of these investigations the writers have limited themselves entirely to those areas with which they are personally familiar, either from a field study or from a study of rock collec- tions. These areas include the North Conway quadrangle, the OssipeeMountains, the Belknap Mountains, Pleasant Mountain in Maine, the Franconia quadrangle, the Percy quadrangle, Tri- pyramid Mountain, and Red Hill. The rock types of each of these * Numbers in parentheses refer to bibliography at end of paper Tesro 1. Dera oN rnn PruroNrc Rocrs or rne Wnrrn Mounrl.rn Macue Sanrrs NAME GABBRO NORITE DIORITE QUARTZ OIOR ITE MONZODIOR ITE MONZONI TE NEPHELITE SYENITE ANALCITE SYENITE TRIPYRAMID MTN TRIPYRAMID MTN. NORTH CONWAY QUAD. FRANCONIA REGION BELXNAP MTNS TRIPYRAMIO MTN, REO AILL PLEASANI MTN DISTRIBUTION BELKNAP MTNS: PLEASANT MTN. PLEASANT MTN. FRANCONIA REGION RtN6-D|XE - 2.5 Mt. SIZE OF BODIES FEW SQ.FT. TO O.25 SQ. MI, NOT XNOWN FEw SQ.FT.TO O.2 Sq.Mt. t.5 sQ. Mt. o.25 TO 2 SO. Mr. OI AMETER NOT KNOWN o.o3sq. Mr. SMALL MSS- O,OI SQ. MI, IRREGULAR SHAPE OF BODIES NOT XNOWN SMALL STOCre AND ROUGHLY CIRCULAR INCOMPLETE RIN6-DIKES IRREGULAR AND RIN6- NOT XNOWN SMALL PERIPBERAL DI KES DI(E BAND ON MAIN STOCK TOTAL AREA AND o.ro sQ.Mt. o.25 SQ.Mt. r.5 sQ.Ml. 4.O SQ. Ml 2.6 Sq- Ml o-o3 sQ. Mt. PER CENT OF YERY SMALL VERY SMALL MAGMA SERIES o.oz Y" o,oss % o.33 7" o.s1 7" g.s1 Y" o.oo7 7" HYPIDIOMORPHICTGRANULAR HYPtOIOMORPHrC, HYPtDtOMORPHTC, TEXTURE BELXNAPS - OIAEASIC HYPt DTOMORPH tC I HYPIDIOMORPHIC. EOUI6RAN- HYPTDtOMORPHTCT HYPI O IOMORPH IC , ALLOTRIOMORPH I C , I NEQU IGRANU LAR I N EqU I GRANU LAR I NEQUI GRANU LAR ULAR TO SUBPORPHYRITIC INEQUIGRANULAR GRANULAR I NEQUI GRANULAR DIAMETER - - - 5 ro MM 3 MM e-3MM. MRK MINEMLS O,5 MM 5 MM 2 5 MM, o.5 - 5 MM OF GRAINS REST 2-SMM, AVG. 2 -3 MM, COLOR DARK GRAY TO BLACX DARK MOTTLED OARK MOTTLED LIGHT 6RAY MOTTLED LIGHT GRAY 6RAY LIGHT oRAY LIGHT GRAY TRIPY. SEL. P.M, F. TRIPY. P, M, LAB. 63.0 49,O AND. 62.0 65.0 AND. 63.0 AND. 72.O ANO. 40.O 47.O oR. 36.0 MP. AO.5 82.O a4.O HBD_ 2Z,O LAB. 55.S af. 17.5 r2.o oR. 2.O oLtG. 6t.o 6r.o MP. - 40.O AB. 37.O oLr6. 3.5 2.s AUG. 14.O I A.O oR. 3.O au6. r5.s 8.o Bt t5.o oR. zt.o 20.o r2.o oR. 40.o NEPH, I4.O ANAL.6.5 6.s 7.5 fL, 6.7 5.O HY. tO.O AP. I.5 TR, HAD. 9.O AUG. 7.O 5.O HBD. t2.O soo. 5.o HBO. 7.5 5.5 4.5 MODE Br. 5.O Dr_ 5.6 MT. 4.O TR qTz. to.o at. 4.o ro.o 3.o Dt. 3.O HBo. 7.O Tt. 4.5 2.5 r.5 Br. 6.0 TI. TR. TR ACC. r.O HBD. 3. O 2.O 7 .O AUG. I,5 ACC. | -O MT. 06 0.5 r.5 oR_ .5 - AP_ 4.4 cHL. r4.O m QTZ. 2.O 4.O Bt. a-o m AF, TR, O.7 TR. acc. o.a 6.0 MT. I t.O ACC. j t_O ACC 2-O 2.O 2.O ACC. 5-O 3.O ZR. TR. TR. TR. roo.o too.o ACC. O.5 roo.5 too o J6oJ rom- rm- roo.o 99.5 M602m acc. - AP.zR. Dt. Br. - too.o ACC. PY,TI- AP, CHL. HY ACC.- HBD. PY. qTZ ACC.- DI AP MT. ZR. ACC.- AP IL. MT TI AEG. MT- CHL, CANCRINITE.WOHLERITE CHEMICAL coMPosrTroN TRIPY. SEL MOOE I MODE I si o2 48.O4 43 -94 46 67 56 66 60.96 Tio? 2.56 4.t3 .55 lo 60 Alz03 20.ro 16.t7 t6.a6 r9.03 2t.36 l9 20 FeaOt 2.32 3.96 9A t.05 FsO 6.13 to.o6 6.37 4. aa 2.04 MnO r 09 TR. ta M9o 4. 6a 5. 05 4.62 a6 .55 r.sz 9.59 s.63 95 Na2O 3.Or 2.93 3.65 4.52 4.66 1.O7 KaO 7g .51 t.26 6.O6 5,54 Hzot 42 42 t2 60 A5 Hao- t3 o2 o ND ZrO2 ND ND NO o2 o7 69 ND o4 ND COz . 09 cl ND ND BaO o6 S oa ND ND o7 .o6 ND r00.06 TOTALS 99.67 I9.5 o0.37 too.o5 99.40 Ag - ALBITE - AND ANDESINE CHL CHLORITE HBD HORN BL E NDE MICROPERTHITE . OLIG OLIGOCLASE RIEg - RIEgECKITE ACC - ACCESSORTES - APATITE DI DIOPSIDE HED HEDEN BERG I TE MAGNETITE OR ORTHOC LAS E SOD - SODALITE AEG - AE6IRINE - ABBREVI AT IONS AST ASTROPHYLLITE FAY FAYALITE HY HYPERSTAENE MAY INCLUDE IL PY PYRITE TI - TITANITE ALL - ALLANITE AUG - AUGITE FL FLUORITE ILMENITE NEPH NEPHELINE PYROX PYROXE NE zA - zrRcoN ANAL - ANALCITE - BIOTITE HAST HASTINGSITE LAA LAgRADOR IT E OL OLIVINE QTZ QUA R TZ QUARTZ QUARTZ SYENITE HASTINGSITE RIEBECKITE NAME SYENITE GRANITE PORPHYRY BIOTITE GRANITE SYENI TE ALBANY TYPE GRANITE GRANITE NORTH CONWAY FRANCONIA REG NORTH CONWAY NORTH CONWAY QUAD. FRANCONIA REGION NORTH CONWAY QUAD NORTH CONWAY QUAD, NORTHCONWAY qUAO, PERCY qUAO. SELKNAP MTNS. REO HILL BELKNAP MTNS BELKNAP DISTRIBUT ION MTNS. PERCY QUAD, PERCY QUAO. OSSIPEEMTNS. FRANCONIA REGION PLEASANT MTN. PERCY OUAO. OSSI PEE MTNS, BELXNAPMTNS. TRIPYRAMIO TRIPYRAMID MTN. FRANCONIA REGION - - - I.5 - - wrDTH O.25 t.S Mt. WIDTHI-3MI STOCKS TO 4.O MILES IN DIAMETER STOCKS: I - 5 MI, IN DIAMETER SIZE OF BODIES o.ro 20.o sQ. Ml r.5 6.0 SQ.Mr. R|NG-DTKES - WrOTH O.25 - LO Mt. OIAMETER-8-9MI, 43:2 SO ML A FEW LENGTH I-4MI. SMALL RING-DIKES SHAPE OF BODIES RIN6-DIKES AND IRREGULAR STOCXS RING-DIKES IRREGULAR RIN6-DIKE N.C - IRREGULAR N.C. -SMALL IRREG. MDIES LARGE STOCXS OF IRREGULAR SHAPE, AND VARY- P - INCOMPLETE RIN6-OIXES P,- INCOMPLETE RING-DIKES ING SIZE. A FEW SMALL RING-DIKES, TOTAL AREA AND 43.r SQ. M 7.5 PER CENT OF SQ. M I 39.9 SQ. M I 43 2 SQ_ M ALL GRANITES 3I5,5 SQ. MI 9.41 y" MAGMA SERIES 7" |.64 6.7t % 9.43 Y" 6A.9 % HYPIDIOMORPHIC, GRANULAR. PORPHYRITIC,GrcUND MASS PORPHYRTTtC, HYPIDIOMORPHTC, HYPtDtOMORPHtC, AYPI DIOMORPH IC. GRANULAR, TEXTURE SOME PORPHYRITIC PANALLOTRIOMORPHIC TO GROUND MASS GRANULAR GRANULAR TO SOME PHASES PORPHYRITIC SOME TRACHYTIC HYPIDIOMORPHIC GRANULAR PA NALLOTR IOMORPH I C MICROPEGMATITIC - - MRK MINERALS: O,5 - I,2 MM GROUNO MAS:0.06 O.3 MM o_5 - to.o MM. GRAIN SIZE o.5 5.O MM PHENOCmTS:5.O -g O MM. o.5 - 3 0 MM o.5 - 3.O MM. REST: r-O - LO MM. PHENOCRYSTSOFTEN UP TO I.5 CM. DARK MINERAS: 0.6- 1.4 MM COLOR GRAY. GREEN, BLUISH DARK @Y, GEEN OR PINK DARK GRAY AND PINK LIGHT GRAY TO WHITE SNOWY WH ITE. MOTTLED PINK TO GREEN. SrcTTED WITH DARK MINERALS BEL, PERCY P.M. TRIPY BEL. N,C. N C, BEL. F AV6. MODE N.C, PERCY N.C. PERCY N.C. BEL. PERCY F. aTz. t.6 3.o Lo QTZ a O 6.3 QTZ t2.6 t5O r3.a QTZ 26.5 QTZ t1 4 Z4.O Qrz 39.4 QTZ 26.7 30.O 230 39.O'34.2 35.r"2s.9 26.5 oR 47.O oR ao o-l MP I se.l MP 23.5 MP I se s MPI -. - 44.4sez ss.slse.e - - I t'" ^, .- l s4.o "" I MP 46.6 a3.O aO.O oLr6 39.oJ oR 174.1 7r.O t7 | oR 349 o,u J o.s o.7 oR > 69-4 64.4 37.01 - | - olf G 42.O 7.O Bt 2.0 O.4 orre J rz.o z.j oLtG | 4 HAST A.3 A.O 5.8 o.'c.J *oJtuo '".