地球科学与环境学报
地毬科學與環境學報
지구과학여배경학보
JOURNAL OF EARTH SCIENCES AND ENVIRONMENT
2015年
3期
1-13
,共13页
石英闪长岩%早白垩世%地球化学%岩石成因%花岗岩%下地壳局部熔融%松潘-甘孜造山带%川西北
石英閃長巖%早白堊世%地毬化學%巖石成因%花崗巖%下地殼跼部鎔融%鬆潘-甘孜造山帶%川西北
석영섬장암%조백성세%지구화학%암석성인%화강암%하지각국부용융%송반-감자조산대%천서북
quartz diorite%Early Cretaceous%geochemistry%petrogenesis%granite%partial melting of lower crust%Songpan-Ganzi orogenic belt%Northwest Sichuan
川西北塔公地区位于青藏高原东部,属于松潘—甘孜造山带的东南部边缘.塔公石英闪长岩侵位于晚三叠世地层中,岩体的 K-Ar 同位素年龄为134~136 Ma,形成于早白垩世.岩石 SiO2质量分数为61．37％~62．25％,铝饱和指数为0．93~0．95,全碱质量分数为5．46％~5．77％,里特曼指数为1．62~1．74,样品属于亚碱性准铝质高钾钙碱系列石英闪长岩.岩石 Mg＃值较高,总体具有高 Sr 含量、低 Nd 含量的同位素地球化学特征.N(87 Sr)/N(86 Sr)值为0．712589~0．713009,初始 N(87 Sr)/N(86 Sr)值为0．709503~0．709878,N (143 Nd)/N(144 Nd)值为0．512135~0．512196,εNd (t)值均为负(－8.6~－7．5),Nd 模式年龄为1．33~1．41 Ga,Hf 模式年龄为1．13~1．37 Ga.该岩体是早白垩世期间,川西北地区陆缘-陆内造山环境下由松潘—甘孜造山带古老的下地壳镁铁质物质局部熔融形成的晚碰撞-碰撞后非分异Ⅰ型花岗岩类.
川西北塔公地區位于青藏高原東部,屬于鬆潘—甘孜造山帶的東南部邊緣.塔公石英閃長巖侵位于晚三疊世地層中,巖體的 K-Ar 同位素年齡為134~136 Ma,形成于早白堊世.巖石 SiO2質量分數為61．37％~62．25％,鋁飽和指數為0．93~0．95,全堿質量分數為5．46％~5．77％,裏特曼指數為1．62~1．74,樣品屬于亞堿性準鋁質高鉀鈣堿繫列石英閃長巖.巖石 Mg＃值較高,總體具有高 Sr 含量、低 Nd 含量的同位素地毬化學特徵.N(87 Sr)/N(86 Sr)值為0．712589~0．713009,初始 N(87 Sr)/N(86 Sr)值為0．709503~0．709878,N (143 Nd)/N(144 Nd)值為0．512135~0．512196,εNd (t)值均為負(－8.6~－7．5),Nd 模式年齡為1．33~1．41 Ga,Hf 模式年齡為1．13~1．37 Ga.該巖體是早白堊世期間,川西北地區陸緣-陸內造山環境下由鬆潘—甘孜造山帶古老的下地殼鎂鐵質物質跼部鎔融形成的晚踫撞-踫撞後非分異Ⅰ型花崗巖類.
천서북탑공지구위우청장고원동부,속우송반—감자조산대적동남부변연.탑공석영섬장암침위우만삼첩세지층중,암체적 K-Ar 동위소년령위134~136 Ma,형성우조백성세.암석 SiO2질량분수위61．37％~62．25％,려포화지수위0．93~0．95,전감질량분수위5．46％~5．77％,리특만지수위1．62~1．74,양품속우아감성준려질고갑개감계렬석영섬장암.암석 Mg＃치교고,총체구유고 Sr 함량、저 Nd 함량적동위소지구화학특정.N(87 Sr)/N(86 Sr)치위0．712589~0．713009,초시 N(87 Sr)/N(86 Sr)치위0．709503~0．709878,N (143 Nd)/N(144 Nd)치위0．512135~0．512196,εNd (t)치균위부(－8.6~－7．5),Nd 모식년령위1．33~1．41 Ga,Hf 모식년령위1．13~1．37 Ga.해암체시조백성세기간,천서북지구륙연-륙내조산배경하유송반—감자조산대고로적하지각미철질물질국부용융형성적만팽당-팽당후비분이Ⅰ형화강암류.
Tagong area of Northwest Sichuan is located in the east of Qinghai-Tibet Plateau,and belongs to the southeast margin of Songpan-Ganzi orogenic belt.The quartz diorites in Tagong area form in Early Cretaceous with K-Ar isotopic ages of 134-136 Ma,and emplace into Late Triassic strata.Mass fractions of SiO2 are 61.37%-62.25%,A/CNK values are 0.93-0.95,mass fractions of total alkali are 5.46%-5.77%,Rittmann indexes are 1.62-1.74,so that the samples belong to subalkaline metaperaluminous high-K calc-alkaline series quartz diorites.The rocks have relative high Mg# values with the isotopic geochemical characteristics of high contents of Sr and low contents of Nd.N (87 Sr)/N (86 Sr)is 0.712 589-0.713 009 with the initial N (87 Sr)/N (86 Sr)of 0.709 503-0.709 878,N (1 43 Nd)/N (1 44 Nd)is 0.5 12 135-0.5 12 1 96 with negativeεNd (t)of -8.6--7.5;Nd and Hf model ages are 1.33-1.41 Ga and 1.13-1.37 Ga,respectively. The quartz diorites belong to undifferentiationⅠ-type granitoids with late- to post-collision caused by partial melting of ancient lower crust mafic materials at the continental margin-intercontinental orogenic setting in Northwest Sichuan.
