Apatite fission track dating of five samples from Cenozoic volcanic strata in the Nimu District in the southern Gangdese Terrane exhibits single population grain ages with a single mean age and associated central ages ranging from 6.8 +/- 0.6 Ma to 9.7 +/- 1.2 Ma. Mean track lengths are between 12.9 +/- 1.7 mu m and 14.2 +/- 2.3 mu m with a single peak characteristic of a single thermal event. The newly documented ages coincide well with the age of high sedimentation rates in the North Tibet Basin that resulted from a 9-5 Ma compressional event. Track length modeling allows three stages to be identified in the sample cooling. The first stage (12-8 Ma) records a period of relative stability with little, if any, cooling at temperatures of 120-110 degrees C suggesting this region had low relief. The second stage (8-2 Ma) reflects rapid cooling with temperatures decreasing from similar to 110 degrees C to surface temperatures of similar to 15 degrees C. This stage can be related to far-field effects of the Himalayan collision, which probably generated the surface uplift and relief that defines the present-day Gangdese Mountains. The mean uplift rate of this period is estimated to be 1.41-0.95 mm/y with total uplift reaching similar to 5900 m. The final stage is related to surface evolution since the Pliocene.

The apatite fission track for 5 samples were obtained. All samples exhibit that the individual grain ages belong to a single population with a single mean age and have central ages from (6.8±0.6) Ma to (9.7±1.2) Ma. Their mean track lengths range between (12.9±1.7) μm and (14.2±2.3) μm with a single peak. These ages well coincide with high sedimentation rates in the basin of north Tibet and resulted from a final compressional event of 9-5 Ma. Modeling identifies three stages in sample cooling history from about 12 Ma to present day. The first stage records a period of relative stability with little if any cooling taking place during more than about 12-8 Ma at the temperature of 120-110 °C. The second stage is requirement for rapid cooling from 8 Ma to 4 Ma with temperature from about 110 °C to surface about 15 °C. Final stage belonged to surface evolution since Pliocene. The second stage linked to the far field effects of the Himalayan collision and most likely generated the surface uplift and relief that define the resent-day Gangdese Mountains. The mean uplifting rate was 1.41 mm/a and the uplift reached 5940 m during the 8-4 Ma.

Synchrotron radiation X-ray fluorescence(SRXRF) microprobe was used in chemical component analysis of single granule apatite crystal from Yu′erya,Hebei province and Dashui district,Gansu province.The result shows that apatites contain many elements including P,Cl,S,K,Ca,Mn,Fe, La,Ce,Nd,Sm,Gd,Yb,Sr,Y,Zr,U and Th and show different characteristics for their origins.Apatites from Yu′erya granite contain higher Mn and Fe,but lower As than those from Dashui.Apatites from these two districts have a great difference in rare earth element(REE) contents.Dashui apatites,I-type granite,show right-inclined pattern with strong LREE enrichment.Yu′erya apatites,S-type granite,show upward-convex chondrite patterns with pronounced depletion of LREE.The results have important implications for identifying different types of granite.And apatite chemistry can be used as an excellent indicator for granite petrogenesis study.

应用裂变径迹技术研究成矿作用是一种新尝试.新疆克朗盆地各个矿区成矿流体包裹体均一温度变化于105～294 ℃,与锆石和磷灰石裂变径迹封闭温度基本一致,所以,裂变径迹方法用于可以应用于成矿作用研究.本文获得不同矿区6个锆石和17个磷灰石裂变径迹分析结果,其中锆石年龄为134 Ma～312 Ma,分属312 Ma,247Ma和158～134 Ma三个年龄组,是3个成矿期的体现;磷灰石年龄为30～130 Ma,是区内成矿作用结束后的热事件时代.因此,成矿作用不仅发生于海西期和印支期,而且发生于燕山期甚至喜山期.

关于土屋-延东铜矿区成矿时代的看法不仅不同,而且均属于海西期.成功获得9个锆石和7个磷灰石的裂变径迹分析结果,其中锆石年龄为158～289Ma,磷灰石年龄为64～140Ma.区内成矿作用亦是同期构造作用的反映,两者相符.鉴于本矿区成矿温度为120～350℃,锆石裂变径迹年龄的封闭温度为250℃,退火带温度为140～300℃,所以,认为锆石裂变径迹年龄可以代表本区的成矿时代.计识别出3个成矿期:289～276,232～200和165～158Ma,表明印支期和燕山期成矿作用的存在.与之相对应,磷灰石裂变径迹年龄为140～132,109～97和64Ma,反映了成矿后100℃左右的时代.3个成矿期从250℃到100℃的持续时间分别为146,108和100Ma左右,具有从早到晚持续时间变小的趋势.裂变径迹模拟表明,具有3阶段地质热历史,其中在白垩纪期间较为稳定,白垩纪之前以及20Ma之后均较快冷却.

In this article, SRXRF technique was applied on apatite, one of accessory minerals from granitic diorite, Ge’erke Gold Deposit. Chemical composition of the crystal and its fluid inclusion was analysized. Apatite composi-tion shows that the original magma belongs to mafic I-type granites with high light rare earth elements and Nd deple-tion characteristics. Containting Fe and Mn and trace As, Co, Zn the fluid inclusion, reflects hydrothermal liquids from magma as one of material resources of gold mineralization.

在新疆阿尔泰造山带所获得的19个锆石裂变径迹年龄变化于155～243 Ma之间,明显地分为2组,分别对应于2个构造活动期,早期为155～189 Ma,晚期为189～243 Ma.这与磷灰石裂变径迹年龄反映的62～100Ma和100～160 Ma两个构造期完全一致.早期和晚期构造活动期持续的时间分别为54～60 Ma和34～38 Ma,而这两个构造期之间的间隔时间,则从早到晚由83～89 Ma变为89～93 Ma.同时,锆石裂变径迹年龄与距特斯巴汗断裂和巴寨断裂的距离有关,反映这两条断裂带对区域构造演化的控制作用.

Fission track ages (FTA) and track lengths of apatite from Qing-He diorite intrusion in Altay Mountains are measured. Apatite fission track ages of three diorite samples is range from (78±5) Ma to (95±5) Ma, and the lengths of horizontal confined spontaneous fission tracks are (13.2±1.2)—(13.5±1.3) μm. The distribution of the track length is narrow and symmetrical with a mean length of approximately 13.3 μm and a standard deviation of around 0.1 μm. The inverse modeling results show that thermal history of this region has four stages, two rapid uplift stages and two stable ones. The rapid uplift during the 115—85 Ma with the cooling rate of 2.2 ℃/ Ma suggests that this region still existed magmatic intrusion and tectonic movements in Yanshanian.

与裂变迹径定年类似,α反冲径迹定年(Alpha-Recoil Track)也是基于天然放射性元素所释放核粒子在固体中产生可蚀刻径迹的积累.铀钍及它们的子体核素进行α衰变时形成α反冲径迹,当发射一个α粒子时,重的剩余核反冲并造成30～40 nm的辐射损失痕迹,经过蚀刻α反冲径迹可在干涉相差显微镜下观测.如果在样品形成以后全部迹径被保留下来,那么测定它们的总数就可以得到样品的年龄.α反冲径迹定年是一种刚刚开始研究的新型热年代学核分析技术,研究样品可以是单个小云母片(约0.5 mm),定年范围102～106 a,该方法对第四纪地质、地理、灾害及考古等领域有很大的应用潜力.

When U,Th and their daughter nuclei emit α particles after α decays,heavy residual nuclei are recoiled,leaving behind a trail of radiation damage in the mineral.The trail of radiation damage is called the nuclear track and can be observed under optical microscope through chemical etching under appropriate conditions.Based on the etching and dating models established,we can obtain both the alpha-recoil track (ART) areal densities and volume densities,as well as the concentrations of U and Th,and then the age of the mineral can be calculated.Alpha-recoil track thermochronology is dominantly used in dating younger samples (106-102 a) and can be widely used in areas of resource environment,geology,archeology and so on.

This paper presents an overview of the fundamentals, techniques, influencing factors, and applications of the apatite (U-Th)/He dating method. (U-Th)/He dating of apatite is a newly developed low-temperature thermochronometry and has been gradually applied to different geological aspects, such as dating, tectonics, geological thermal history and paleotopography. The closure temperature of the apatite (U-Th)/He age is only about 75℃, which is lower than that of any other known technique, suggesting that apatite He age provides some information on the final stages of cooling. By combining apatite (U-Th)/He with other methods such as feldspar multidomain thermochronometry and fission track technique, more detailed and robust cooling histories may be obtained. Compared with other techniques, the attractions of the apatite He method lie in sensitivity to previously inaccessible temperature ranges, high precision and less sample mass. Although this technique remains at the developing stage, it may after all be accepted as a quite effective method for the low-temperature thermochronology. It is noted that this field is growing rapidly, and what is presented in this paper is likely to be superseded in the coming years.

The Dashui gold deposit is located in the south of West Qinling Mountains between Qinling orogenic zone and Songpan-Ganzi orogenic zone. The mineralization can be divided into the primary ore-forming stage and the supergene oxidation-secondary enrichment stage. Lying in the west Qinling orogenic belt,the deposit is controlled by the NWW-trending fault zone. The host rocks of the gold mineralization are mainly Triassic altered limestone and adamellite dikes. The δ 34 S values of pyrite range from -1.8 to +4.5 per mil with a mean of 2.40‰,reflecting a deep source of sulfur. Oxygen isotope data of calcite from ores indicate that calcite has δ 18 O values ranging from -22.4 to -11.1 per mil. The calculated δ 18 O water values of calcite range from -4.32 to +8.33 per mil and the δD values range from -61.1 to -101 per mil,suggesting that the ore fluids were mainly derived from the magma at the early stage of mineralization. Nevertheless,the values at the late ore-forming stage decrease,indicating the mixture of meteoric waters at the time of mineralization. Homogenization temperatures of fluid inclusions are relatively low,varying from 100 to 400 ℃ and mostly in the range of 150～200 ℃,with a peak value of 175 ℃. Salinities exhibit a wide range from 2.70 to 9.10 wt.% NaClequiv.,with a mean of 4.88 wt.% NaClequiv. In addition,the early gold mineralization occurred between 196 Ma and 182.8 Ma,and the late gold mineralization took place between 72.15 Ma and 41.21 Ma,as shown by the Rb-Sr isochron dating of inclusions from calcite in ores. This means that the Dashui gold deposit has at least two gold ore-forming stages.

通过对新疆阿尔泰铁热克提岩体4个磷灰石裂变径迹样品分析研究表明,具有3个阶段的热演化模式:①大约 120 Ma之前,温度为105～130 ℃或90～120 ℃,属于较高温稳定期;②60～120 Ma,温度为90～120 ℃或20～65 ℃,系快速冷却与隆升期;③60 Ma以来为20～65 ℃或12～18 ℃,属低温稳定期.第2阶段(60～90 Ma期间),冷却速率为2.5～3.23 ℃/Ma,相当于抬升速率为83.3～107.7 m/Ma.60～120 Ma的快速隆升作用以及80.4～91.9 Ma的裂变径迹年龄,证实燕山晚期发生过新的陆内挤压造山活动.

从对新疆阿尔泰造山带西部构造活动的研究中获得一批较为系统的磷灰石裂变径迹分析结果.32个磷灰石裂变径迹年龄为(163.0±6.4)～(46.9±7.2) Ma,平均径迹长度为(14.5±0.1)～(11.3±0.4) μm,长度标准差为1.4～2.7 μm.区内具有3阶段热历史:约110 Ma之前处于约100～120 ℃较高温稳定阶段,然后在约110～40 Ma期间发生快速冷却与隆升事件,从约40 Ma开始发生另一较为缓慢的冷却事件.总体上自北而南,剥蚀速率和冷却速率均逐渐变小.文中裂变径迹资料表明,阿尔泰山西段主要断裂带现在向南倾斜,区内构造演化亦主要受Tesbahan、Kulti和Basei三条断裂带逆冲热事件的控制.