地质通报
地質通報
지질통보
GEOLOGICAL BULLETIN OF CHINA
2015年
8期
1541-1549
,共9页
魏运许%赵小明%杨金香%徐大良%刘圣德%廖宗明%邓新
魏運許%趙小明%楊金香%徐大良%劉聖德%廖宗明%鄧新
위운허%조소명%양금향%서대량%류골덕%료종명%산신
球状岩%球状花岗闪长岩%扬子陆核%结晶作用%黄陵
毬狀巖%毬狀花崗閃長巖%颺子陸覈%結晶作用%黃陵
구상암%구상화강섬장암%양자륙핵%결정작용%황릉
orbiculite%orbicular granodiorite%Yangtze continental nucleus%crystallization%Huangling
在扬子陆块核部黄陵地区发现具球状构造的花岗闪长岩。岩石产于新元古代斑状花岗闪长岩与石英闪长岩之间,出露面积极小。球状花岗闪长岩岩体由主岩、球状体及球间基质三部分组成,球状体呈圆形、椭圆形及不规则状,由球核和同心球壳组成,球体大小多为5~12cm。依据球壳及球核的差异,可大致分为具有多壳层同心结构、具单壳层结构、无明显壳层结构3种类型的球状体。单壳层球壳由角闪石、黑云母等暗色矿物含量高的暗色层组成,具放射状构造;多壳层球壳由含角闪石、黑云母等暗色矿物的暗色层和基本不含或含少量暗色矿物、以斜长石为主的浅色层组成韵律层,具梳状、放射状构造;球核成分可以是同源岩浆组分,也可以是异源捕虏体。单壳层球体,球核、球壳、基质的斜长石牌号依次为36、32、26,酸性程度不断增加,内部呈放射状生长,反映其可能由内向外经岩浆结晶作用形成。初步认为多壳层球体球壳富韵律的变化为富含气水热液的岩浆在动荡的环境下结晶形成,球壳中矿物结晶顺序可能由外向内,核部结晶时间相对更长。
在颺子陸塊覈部黃陵地區髮現具毬狀構造的花崗閃長巖。巖石產于新元古代斑狀花崗閃長巖與石英閃長巖之間,齣露麵積極小。毬狀花崗閃長巖巖體由主巖、毬狀體及毬間基質三部分組成,毬狀體呈圓形、橢圓形及不規則狀,由毬覈和同心毬殼組成,毬體大小多為5~12cm。依據毬殼及毬覈的差異,可大緻分為具有多殼層同心結構、具單殼層結構、無明顯殼層結構3種類型的毬狀體。單殼層毬殼由角閃石、黑雲母等暗色礦物含量高的暗色層組成,具放射狀構造;多殼層毬殼由含角閃石、黑雲母等暗色礦物的暗色層和基本不含或含少量暗色礦物、以斜長石為主的淺色層組成韻律層,具梳狀、放射狀構造;毬覈成分可以是同源巖漿組分,也可以是異源捕虜體。單殼層毬體,毬覈、毬殼、基質的斜長石牌號依次為36、32、26,痠性程度不斷增加,內部呈放射狀生長,反映其可能由內嚮外經巖漿結晶作用形成。初步認為多殼層毬體毬殼富韻律的變化為富含氣水熱液的巖漿在動盪的環境下結晶形成,毬殼中礦物結晶順序可能由外嚮內,覈部結晶時間相對更長。
재양자륙괴핵부황릉지구발현구구상구조적화강섬장암。암석산우신원고대반상화강섬장암여석영섬장암지간,출로면적겁소。구상화강섬장암암체유주암、구상체급구간기질삼부분조성,구상체정원형、타원형급불규칙상,유구핵화동심구각조성,구체대소다위5~12cm。의거구각급구핵적차이,가대치분위구유다각층동심결구、구단각층결구、무명현각층결구3충류형적구상체。단각층구각유각섬석、흑운모등암색광물함량고적암색층조성,구방사상구조;다각층구각유함각섬석、흑운모등암색광물적암색층화기본불함혹함소량암색광물、이사장석위주적천색층조성운률층,구소상、방사상구조;구핵성분가이시동원암장조분,야가이시이원포로체。단각층구체,구핵、구각、기질적사장석패호의차위36、32、26,산성정도불단증가,내부정방사상생장,반영기가능유내향외경암장결정작용형성。초보인위다각층구체구각부운률적변화위부함기수열액적암장재동탕적배경하결정형성,구각중광물결정순서가능유외향내,핵부결정시간상대경장。
The orbicular granodiorite outcropped between Neoproterozoic phyric granodiorite and quartz diorite in an extremely small place of Huangling area, the Yangtze continental nucleus, was discovered for the first time. This kind of orbicular granodiorite is composed of host rock, orbs and matrix among orbs. Though the orbs are round, oval or irregular in shape, they are all composed of nuclear bulges and concentric shells. Based on the discrepancies of their nuclear bulges and spherical shells, the authors divide the orbs into three types, i.e., orbs with multiple shell layers and concentric structure, orbs with single shell layer structure, and orbs with no obvious structure of shell layers. Composed of dark layers with dark minerals like amphibole and biotite, the single shell layer exhibits radial structure. However, the shell of multiple shell layers is composed of rhythmites comprising layers of dark minerals like amphi?bole and biotite as well as light-color layers comprising dominantly plagilclase with no or very few dark minerals, exhibiting comb or radial structure. The composition of nuclear bulge might have come from comagma or heterogeneous xenolith, amphibolite and en?claves rich in mica. In the orbs with single shell layer, the acidity increases constantly from nuclear bulge through shell to matrix, and the inner part grows in radial patterns, indicating the growth of magmatic crystallization from the inner part to the outer part. As for the rhythmites in the orbs with multiple shell layers, the authors preliminarily hold that they might have resulted from the crystalliza?tion of magma rich in hydrothermal solution in a turbulent environment, the minerals in the shell might have crystallized from the in?ner part to the outer part, and the crystallization of nuclear bulges lasted relatively longer time.