東準噶爾卡拉麥里斷裂以南幔源底侵體、“釘合花崗巖體”的發(fā)現(xiàn)及其地質意義
發(fā)布時間：2018-10-18 16:03
【摘要】：新疆富蘊縣滴水泉-畜牧辦侵入體出露于卡拉麥里斷裂以南,呈北西西向帶狀分布,以堿長花崗巖體為主,也可見規(guī)模較小的角閃輝長巖體。堿長花崗巖體的巖石組合為堿長花崗斑巖+堿長花崗巖,高硅(SiO_2=71.07%~76.71%),富堿(Na_2O+K_2O=7.41%~9.07%)、K_2ONa_2O(平均為1.10),顯示出A型花崗巖的特點。角閃輝長巖體涌動侵入于堿長花崗巖體之中,二者接觸帶附近發(fā)育漿混性質的石英閃長巖。輝長巖+花崗巖的雙峰式巖石組合、構造判別圖解R2-R1及區(qū)域地質背景指示滴水泉侵入體形成于陸內伸展環(huán)境,且花崗巖體具有"釘合巖體"的作用,穿插了卡拉麥里蛇綠巖帶。結合巖體的LA-ICP-MS鋯石年齡(堿長花崗巖的206Pb/238U加權平均年齡為321±2Ma,角閃輝長巖的206Pb/238U加權平均年齡為319±3Ma)可知,卡拉麥里洋盆在晚石炭世早期(321Ma)之前已經閉合。同位素及微量元素特征顯示,堿長花崗巖為年輕地殼部分熔合融的產物,而角閃輝長巖則來源于虧損的軟流圈地幔及俯沖交代的地幔楔物質,代表了同期花崗巖的底侵巖漿演化的產物。輝長巖與花崗巖相似的εNd(t)值及明顯的巖漿混合作用表明該區(qū)的花崗巖體并非來源于底侵巖漿的高度分異或底侵體的部分熔融,而最可能為底侵體之上的年輕地殼的部分熔融,這一結論與最近一些學者研究的斷裂以北的花崗巖體成因機制相同。晚石炭世早期幔源底侵體的發(fā)現(xiàn),為卡拉麥里地區(qū)后碰撞花崗巖類的幔源底侵作用提供了可靠的地質依據。
[Abstract]:The Dishui Quan-Livestock Office intrusive body in Fuyun County Xinjiang is exposed to the south of the Kalamaili fault and distributes in the north west and west direction with the alkali feldspar granite as the main body and the smaller hornblende gabbro body. The alkali feldspar granite is composed of alkali-feldspar porphyry, high SiO_2=71.07%~76.71%, Na_2O K _ 2O _ 1 7.41 ~ 9.07% and K_2ONa_2O (an average of 1.10), showing the characteristics of A-type granite. The hornblende gabbro intruded into the alkali feldspar granite and magma mixed quartz diorite was developed near the contact zone between the two bodies. The bimodal rock assemblage of gabbro granites, the tectonic discriminant R2-R1 and the regional geological background indicate that the Dishui spring intrusion was formed in the intracontinental extensional environment, and the granite body has the function of "nailing rock mass", which is inserted into the Kalamaili ophiolite belt. Combined with the LA-ICP-MS zircon age (206Pb/238U weighted mean age of 321 鹵2Mafor alkali feldspar granites and 319 鹵3Ma for hornblende gabbro), the Kalamori ocean basin was closed prior to the early late Carboniferous (321Ma). Isotopic and trace element characteristics indicate that alkali feldspar granite is the product of partial fusion of young crust, while hornblende gabbro is derived from depleted asthenospheric mantle and subducted mantle wedge material. It represents the product of the evolution of underplating magma in the same period of granite. The similar 蔚 Nd (t) values of gabbro to granite and obvious magmatic mixing indicate that the granitic bodies in this area are not derived from the high differentiation of the underplating magma or from the partial melting of the underplating magma, but most likely from the partial melting of the young crust above the underplating magma. This conclusion is the same as the genetic mechanism of the granite body north of the fault studied recently by some scholars. The discovery of mantle-derived transgressions in the early late Carboniferous provides a reliable geological basis for mantle-derived transgressions of post-collisional granites in the Kalamaili area.
【作者單位】： 中國地質大學地球科學學院;天津地質礦產研究所;中國地質大學地質過程與礦產資源國家重點實驗室;
【基金】：中國地質調查局計劃項目(1212011120508)資助
【分類號】：P588.12
[Abstract]:The Dishui Quan-Livestock Office intrusive body in Fuyun County Xinjiang is exposed to the south of the Kalamaili fault and distributes in the north west and west direction with the alkali feldspar granite as the main body and the smaller hornblende gabbro body. The alkali feldspar granite is composed of alkali-feldspar porphyry, high SiO_2=71.07%~76.71%, Na_2O K _ 2O _ 1 7.41 ~ 9.07% and K_2ONa_2O (an average of 1.10), showing the characteristics of A-type granite. The hornblende gabbro intruded into the alkali feldspar granite and magma mixed quartz diorite was developed near the contact zone between the two bodies. The bimodal rock assemblage of gabbro granites, the tectonic discriminant R2-R1 and the regional geological background indicate that the Dishui spring intrusion was formed in the intracontinental extensional environment, and the granite body has the function of "nailing rock mass", which is inserted into the Kalamaili ophiolite belt. Combined with the LA-ICP-MS zircon age (206Pb/238U weighted mean age of 321 鹵2Mafor alkali feldspar granites and 319 鹵3Ma for hornblende gabbro), the Kalamori ocean basin was closed prior to the early late Carboniferous (321Ma). Isotopic and trace element characteristics indicate that alkali feldspar granite is the product of partial fusion of young crust, while hornblende gabbro is derived from depleted asthenospheric mantle and subducted mantle wedge material. It represents the product of the evolution of underplating magma in the same period of granite. The similar 蔚 Nd (t) values of gabbro to granite and obvious magmatic mixing indicate that the granitic bodies in this area are not derived from the high differentiation of the underplating magma or from the partial melting of the underplating magma, but most likely from the partial melting of the young crust above the underplating magma. This conclusion is the same as the genetic mechanism of the granite body north of the fault studied recently by some scholars. The discovery of mantle-derived transgressions in the early late Carboniferous provides a reliable geological basis for mantle-derived transgressions of post-collisional granites in the Kalamaili area.
【作者單位】： 中國地質大學地球科學學院;天津地質礦產研究所;中國地質大學地質過程與礦產資源國家重點實驗室;
【基金】：中國地質調查局計劃項目(1212011120508)資助
【分類號】：P588.12
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