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Chronology of Emplacement of Mesozoic Batholithic Complexes in California and Western Nevada by J

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Chronology of Emplacement of Mesozoic Batholithic Complexes in California and Western Nevada by J Chronology of Emplacement of Mesozoic Batholithic Complexes In California and Western Nevada By J. F. EVERNDEN and R. W. KISTLER GEOLOGICAL SURVEY PROFESSIONAL PAPER 623 Prepared in cooperation with the University of California (Berkeley) Department of Geological Sciences UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1970 UNITED STATES DEPARTMENT OF THE INTERIOR WALTER J. HICKEL, Secretary GEOLOGICAL SURVEY William T. Pecora, Director Library of Con;gress CSJtalog-card No. 7s-.60.38'60 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 - Price $1.25 (paper cover) CONTENTS Page Abstract-------------------------------~---------------------------------------------------------------------- 1 Introduction--------------------------------------------------------------------------------~----------------- 1 Analyt:cal problems ____________________ -._______________________________________________________________________ 2 Analytical procedures______________________________________________________________________________________ 2 Precision and accuracy ___________________ -.- __ _ _ _ _ __ _ _ _ __ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 2 Potassium determinations_______________________________________________________________________________ · 2 Argon determinations--------~------------------~------------------------------------------------------ 5 Chemical and crystallographic effects on potassium-argon ages----------.----------------------------------------- 6 Apparent age as a function of c.hlorite content of biotite __________________ -------___________________________ 6 Apparent age as a function of mineral type ______________________ ·----------------------------------------- 7 Apparent potassium-argon ages of quartz from granitic rocks _________________________________ ----------_____ 7 Geologic interpretation __ ---- ________________ ----- ______________ ------- __________________ ------ _________ ·________ 9 Genetic significance of potassium-argon ages of biotite and hornblende _______________________ ·_________ - ___ ----____ 9 Potassium-argon age in plutons of Cathedral Peak type----------------------------------------------------- 9 Depth of emplacement of the Sierran plutons-------:------------------------------------·------------------- 12 Discordant biotite-hornblende pairs-evidence of rehea~d plutons ____ -------________________________________ 15 Concordant biotite-hornblende pairs-evidence of the age of an intrusive event________________________________ 16 Growth of the Sierra Nevada batholith ______________________________________________________________ -____ 16 Cathedral Range intrusive epoch of·Late Cretaceous age _______ : ___________________ .:-----------~-------- 17 Huntington Lake intrusive epoch of Early Cretaceous age _________ -_- _____________________ -_- __ --_-____ 17 Yosemite intrusive epoch of Late Jurassic age--------------------------------------------------------- 17 Inyo Mountains intrusive epoch of Early and Middle Jurassic age-----------------------~·--------------- 18 Lee Vining intrusive epoch of Middle and Late Triassic age--------------------------------------------- 19 Summary of ages in all intrusive epochs _______________________ ~_- ______________________ -- ____ ---- ___ - 19 Uplift of plutons of the transverse and Coast Ranges-------------------------------------·---------------------- 21 Granite emplacement and sedimentation on the continent------------------------------------------------------- 22 Correspondence of intrusive and deformational events in the Sierra Nevada _________________________ --- ___ ---- __ -- 25 Conclu~ons------------~-------------------------------------------------------------------------------------- 26 References cited-------~------------ 7 -------------------------------------------------------------------------- 26 ILLUSTRATIONS Page PL,\'l'E 1. Map showing distribution of Mesozoic granitic rocks in California and western Nevada _____ ------------- In pocket 2. Map showing potassium-argon age of biotite and (or) hornblende for each locality shown on plate L __ ---- In pocket Histograms of 8(.z- > values _________________________________________________ .:. ____________ ------------- 3 FIOUll.E 1. 11 2. Sketch map showing potassium-argon dates on samples from plutons of Cathedral Peak type, Sonora and Cathedral Peak plutons----------------------------------------------------------------------------------- 10 3. Sketch map showing potassium-argon dates on samples from plutons of Cathedral Peak type, Recess and Whitney plutons _______________ .:.---------------------------------------------~-------.:.------------------ 11 4. Graph showing pressure-temperature fields for metamorphic mineral and rock pairs ________ ----------------- 13 5. Graphic representation of heat model for intrusive rocks of the Sierra Nevada_________________ - ____ ---- __ -- 14 6. Rubidium-strontium isochron plots for granitic rocks in California ________________________________ ----____ 18 7. Diagram showing potassium-argon mineral ages and rubidium-strontium whole-rock ages for the Lee Vining, Yosemite, Huntington Lake and Cathedral Range intrusive epochs ___________________________ --_-____ 20 H. Diagram showing potassium-argon mineral ages and ru.bidium-strontium whole-rock ages for granitic rocks of the lnyo Mountains, Yosemite, Huntington Lake, and Cathedral Range intrusive epochs________________ 21 n. Diagram showing relation of sedimentation in the Sacramento Valley to granite emplacement in the Sierra Nevadaarea------------------------------------------------------------------------------------ 23 10. Curve showing extent of epicontinental seas and Mesozoic and Cenozoic time scale __________________ -_- __ -_ 24 III IV CONTENTS TABLES Page TABLE 1. Potassium-argon ages of minerals with duplicate argon analyses__________________________________________ 5 2. Data showing variation of potassium-argon age with variation in chlorite content in biotite__________________ 6 3. Multimineral analyses (of same rock)----------------------------------------------------------------- 8 4. Rubidium-strontium analytical data ____ ·______________________________________________________________ 19 5. Potassium-argon analyses and location of sample localities----------------------~------------------------ 31 6. Rock name and description of sample locality__________________________________________________________ 35 CHRONOLOGY OF EMPLACEMENT OF MESOZOIC BATHOLITHIC COMPLEXES IN CALIFORNIA AND WESTERN NEVADA By J. F. EVERNDEN 1 and R. W. KisTLER ABSTRACT ages." Accepting this as the only possible meaning to Ar40/K40 was determined for minerals from specimens of Meso­ be signified by plus or minus estimates on determined zoic granitic rocks collected at 250 localities in California and "ages," there is very little documentation of factors western Nevada. Analytical reproducibility of Ar40/K40 in com­ influencing such plus or minus estimates. Moreover, mon minerals from granitic rocks was tested in the la·boratories highly variable statements are still made by different of t'he U.S. Geological Survey and University of California (Berkeley), and the results were studied for interpretation of investigators with little or no supporting data. Some the genetic significance of potassium-argon ages derived from investigators report ages with "probable errors of about the rrutios. 5.'percent," while others imply precision of 1 percent. The potassium-argon ages of minerals from Mesozoic granitic The data of the present paper clearly show the influence rocks in California have a continuity from 210 to. 80 million of diverse factors on precision and accuracy of years ago. However, a distinct periodicity of magma generation nnd intrusion is shown when the ages are related to the distribu­ potassium-argon ages. The investigation of determined tion of·genetic groups of plutons based on geologic mapping. Five potassium-argon ratios as a function of mineral altera­ epochs of magma generation and emplacement that took from tion or other factors has indicated the necessity of con­ 10 to 15 million years to complete were initiated at approxi­ sidering such factors in the interpretation of derived mately 30-million year intervals. Each intrusive epoch was "ages." preceded by, or was in part contemporaneous with, a period of regional deformation in California or western Nevada. These Data previously presented ( Evernden and Richards, intrusive epochs and their ages are: 1962) on the Paleozoic batholiths of eastern Australia strongly suggested that there had been continuity of Maximum to minimum age granite generation and emplacement over a period of (m.fl.) Geologic age Intrusive epoch 9Q-79. ___ --- _ Late Cretaceous ___________ Cathedral some 200 million years. The locus of batholithic intru­ Range. sion moved more than 300 km, but the "ages" obtained 121-104. _ _ _ _ _ _ Early Cretaceous__________ Huntington implied the virtual lack of any cessation of emplace­ Lake. ment of granitic magma during that long interval. On 148-132. _:..- ___ L.ate Jurassic _____________ Yosemite. the other hand, previous interpretations of ages of 180-160 _______ Early and Middle Jurassic __ lnyo Mountains. 21Q-195 _______ Middle and Late Triassic ___ Lee Vining. granitic rocks from the Sierra Nevada of California have implied at least two distinct periods of granite INTRODUCTION emplacement (Curtis and others, 1958).
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