南極月球隕石MIL05035礦物學、巖石學及演化歷史
發(fā)布時間：2018-09-04 10:56
【摘要】：月球隕石MIL05035巖石類型上屬于普通輝石低鈦玄武巖,粗粒輝長結構,無角礫化。主要礦物為輝石(60.2%)、斜長石(27.3%)和橄欖石(6.05%),次要礦物為石英(4.36%)、鈦鐵礦(1.25%)和隕硫鐵(0.84%),含極少量富Ti、Fe尖晶石和磷灰石,廣泛發(fā)育由鈣鐵輝石+鐵橄欖石+石英組成的后成合晶三相集合體。輝石顆粒具有明顯的化學成分不均勻性和出溶片晶,核部相對貧鐵鈣富鎂(Fs30.2-60.8Wo14.2-35.0),邊部富鐵鈣貧鎂(Fs47.5-64.9Wo22.8-44.3)。熔長石化斜長石具有微弱的成分環(huán)帶,邊部相對富堿金屬元素(Ab9.3-12.3,Or0.31-1.03),核部則相反(Ab7.6-10.6,Or0.12-0.36),含有未熔長石化的殘留斜長石。橄欖石具有粗晶橄欖石(Fa95.5-96.6)和后成合晶中細粒橄欖石(Fa88.9-93.5)兩種產狀。石英具有脈狀、團塊狀和蠕蟲狀等產狀:脈狀石英大部分轉變?yōu)槎趸璨Ａ?核部石英具有較寬的拉曼譜特征峰(448~502cm-1),證明其經歷了沖擊變質與退變質作用;團塊狀石英分布于粗粒橄欖石顆粒間或橄欖石與斜長石和輝石接觸邊界上,與斜長石構成充填結構;蠕蟲狀石英分布于細粒后成合晶中。粗粒輝石邊部鐵輝石和后成合晶中輝石成分的繼承性、結構上的延續(xù)性、光學特征上的沖擊暗化現(xiàn)象、與沖擊熔脈結構上的相關性和后成合晶中發(fā)育與粗粒輝石方向幾乎一致的解理等方面的證據,認為后成合晶可能由于鐵輝石在沖擊壓力釋放與溫度降低后的退變質作用下分解形成。根據巖石礦物結構觀察、成分分析和MELTS模擬表明該隕石母巖的巖漿演化過程可能為:母巖漿在溫度降低后首先產生極少量鈦鐵尖晶石、其次是普通輝石和鈣長石先后結晶;隨著溫度下降,貧鈣鐵普通輝石、鐵鈣鐵輝石和鐵普通輝石等在普通輝石邊部大量結晶,鈣長石邊部分異結晶少量培長石或拉長石;隨著溫度繼續(xù)下降,早期結晶的普通輝石析出易變輝石等出溶片晶,橄欖石在輝石和斜長石邊部結晶;其后,鈦鐵礦和隕硫鐵析出,石英沿橄欖石和鈣長石等先結晶礦物裂隙充填。出露月表后強烈的沖擊變質作用使斜長石幾乎全部轉變?yōu)槿坶L石、石英大部分轉變?yōu)槎趸璨Ａ?并具有一系列面狀變形,沖擊熔脈發(fā)育,沖擊變質程度至少為S5。本研究為月球的巖漿演化和沖擊變質過程提供了重要證據。
[Abstract]:The MIL05035 rock type of lunar meteorite belongs to ordinary pyroxene low titanium basalt with long structure of coarse grain and no breccia. The main minerals are pyroxene (60.2%), plagioclase (27.3%) and olivine (6.05%), secondary minerals are quartz (4.36%), ilmenite (1.25%) and meteorite (0.84%), and contain a very small amount of Ti,Fe rich spinel and apatite. The post-eutectic three-phase aggregates composed of calcium-ferroxene iron olivine quartz are widely developed. The pyroxene particles have obvious chemical composition inhomogeneity and exsolution tablets, the core is relatively poor in iron, calcium and magnesium (Fs30.2-60.8Wo14.2-35.0), and the edge part is rich in iron, calcium and magnesium (Fs47.5-64.9Wo22.8-44.3). The feldspar plagioclase has a weak composition ring with relatively alkali rich metal elements (Ab9.3-12.3,Or0.31-1.03) in the edge and Ab7.6-10.6,Or0.12-0.36 in the nucleus, which contains the residual plagioclase from the unmelted petrifaction. Olivine has two types of occurrences: coarse olivine (Fa95.5-96.6) and fine olivine (Fa88.9-93.5) in post-syntectic crystal. Most of the vein-like quartz is converted to silica glass, and the nuclear quartz has a wide Raman spectrum characteristic peak (448~502cm-1), which indicates that the quartz has undergone impact metamorphism and retrograde metamorphism. Block quartz distributes between coarse olivine grains or olivine contact boundary with plagioclase and pyroxene and forms filling structure with plagioclase while wormlike quartz distributes in fine post-grain eutectic. The inheritance of pyroxene composition, the continuity of structure, and the impact darkening of optical characteristics in the edge of the coarse pyroxene and the post eutectic. Evidence of the correlation with the structure of the impact melting pulse and the cleavage of the development of coarse-grained pyroxene in the post-eutectic, It is considered that the post-eutectic may be due to the decomposition and formation of ferroxene due to the retrograde metamorphism of impingement pressure release and temperature reduction. According to the observation of rock mineral structure, the composition analysis and MELTS simulation indicate that the magmatic evolution process of the meteorite parent rock may be as follows: the mother magma first produces a very small amount of titaniferrite after lowering the temperature, and then the ordinary pyroxene and calcium feldspar crystallize successively; With the decrease of temperature, the poor calcium iron ordinary pyroxene, the iron calcium iron pyroxene and the iron ordinary pyroxene crystallized in a large number at the edge of the ordinary pyroxene, and a small amount of heterocrystalline or elongate on the side of the calcium feldspar; The early crystallized ordinary pyroxene precipitated with volatile pyroxene, and olivine crystallized at the edge of pyroxene and plagioclase, then ilmenite and meteorite precipitated, and quartz was filled with cracks along the first crystalline minerals such as olivine and calcium feldspar. The strong impact metamorphism made the plagioclase transform into meltmorillonite almost entirely, and most of the quartz changed into silica glass, with a series of surface deformation, the impact melting vein developed, and the impact metamorphism degree was at least S5. This study provides important evidence for magmatic evolution and impact metamorphism on the moon.
【作者單位】： 桂林理工大學 廣西隱伏金屬礦產勘查重點實驗室;桂林理工大學地球科學學院;
【基金】：國家自然科學基金項目(41173077) 廣西隱伏金屬礦產勘查重點實驗室主任基金項目(13-A-01-02)聯(lián)合資助
【分類號】：P185.83;P588.145
[Abstract]:The MIL05035 rock type of lunar meteorite belongs to ordinary pyroxene low titanium basalt with long structure of coarse grain and no breccia. The main minerals are pyroxene (60.2%), plagioclase (27.3%) and olivine (6.05%), secondary minerals are quartz (4.36%), ilmenite (1.25%) and meteorite (0.84%), and contain a very small amount of Ti,Fe rich spinel and apatite. The post-eutectic three-phase aggregates composed of calcium-ferroxene iron olivine quartz are widely developed. The pyroxene particles have obvious chemical composition inhomogeneity and exsolution tablets, the core is relatively poor in iron, calcium and magnesium (Fs30.2-60.8Wo14.2-35.0), and the edge part is rich in iron, calcium and magnesium (Fs47.5-64.9Wo22.8-44.3). The feldspar plagioclase has a weak composition ring with relatively alkali rich metal elements (Ab9.3-12.3,Or0.31-1.03) in the edge and Ab7.6-10.6,Or0.12-0.36 in the nucleus, which contains the residual plagioclase from the unmelted petrifaction. Olivine has two types of occurrences: coarse olivine (Fa95.5-96.6) and fine olivine (Fa88.9-93.5) in post-syntectic crystal. Most of the vein-like quartz is converted to silica glass, and the nuclear quartz has a wide Raman spectrum characteristic peak (448~502cm-1), which indicates that the quartz has undergone impact metamorphism and retrograde metamorphism. Block quartz distributes between coarse olivine grains or olivine contact boundary with plagioclase and pyroxene and forms filling structure with plagioclase while wormlike quartz distributes in fine post-grain eutectic. The inheritance of pyroxene composition, the continuity of structure, and the impact darkening of optical characteristics in the edge of the coarse pyroxene and the post eutectic. Evidence of the correlation with the structure of the impact melting pulse and the cleavage of the development of coarse-grained pyroxene in the post-eutectic, It is considered that the post-eutectic may be due to the decomposition and formation of ferroxene due to the retrograde metamorphism of impingement pressure release and temperature reduction. According to the observation of rock mineral structure, the composition analysis and MELTS simulation indicate that the magmatic evolution process of the meteorite parent rock may be as follows: the mother magma first produces a very small amount of titaniferrite after lowering the temperature, and then the ordinary pyroxene and calcium feldspar crystallize successively; With the decrease of temperature, the poor calcium iron ordinary pyroxene, the iron calcium iron pyroxene and the iron ordinary pyroxene crystallized in a large number at the edge of the ordinary pyroxene, and a small amount of heterocrystalline or elongate on the side of the calcium feldspar; The early crystallized ordinary pyroxene precipitated with volatile pyroxene, and olivine crystallized at the edge of pyroxene and plagioclase, then ilmenite and meteorite precipitated, and quartz was filled with cracks along the first crystalline minerals such as olivine and calcium feldspar. The strong impact metamorphism made the plagioclase transform into meltmorillonite almost entirely, and most of the quartz changed into silica glass, with a series of surface deformation, the impact melting vein developed, and the impact metamorphism degree was at least S5. This study provides important evidence for magmatic evolution and impact metamorphism on the moon.
【作者單位】： 桂林理工大學 廣西隱伏金屬礦產勘查重點實驗室;桂林理工大學地球科學學院;
【基金】：國家自然科學基金項目(41173077) 廣西隱伏金屬礦產勘查重點實驗室主任基金項目(13-A-01-02)聯(lián)合資助
【分類號】：P185.83;P588.145
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本文編號：2221874
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