黑龙江省多宝山Cu-Mo矿床成矿斑岩锆石U-Pb年龄及地球化学特征

多宝山矿床位于大兴安岭北部,是中国东北地区规模最大的斑岩型Cu-Mo矿床。文章对该矿床中与成矿关系密切的花岗闪长斑岩进行了详细的LA-ICP-MS锆石U-Pb定年、主量元素、微量元素及Hf同位素研究。结果表明,花岗闪长斑岩的LA-ICP-MS锆石U-Pb年龄为(474.9±1.8)Ma,其w(Si O2)为70.73%~73.45%,w(K2O)和w(Na2O)分别为2.99%~3.88%、3.86%~4.38%,属高钾钙碱性系列。岩石富集轻稀土元素,(La/Yb)N=6.32~12.76,显示出Ba、K、La、Sr、Zr、Hf、Sm等元素富集,Th、Ta、Nb、Ce、P、Ti等元素亏损的特征。锆石εHf(t)值介于10.3~14.6。详尽的元素和同位素地球化学特征表明多宝山花岗闪长斑岩可能形成于大陆边缘弧环境,来源于加厚陆壳条件下亏损地幔新增生的年轻地壳物质的部分熔融过程。     

中天山南缘伊尔根布鲁克石英闪长岩锆石U-Pb年龄和地球化学特征

中天山位于天山造山带核心部位,对研究中亚造山带西南段构造演化、块体起源和陆壳生长等具重要意义。本次研究围绕中天山伊尔根布鲁克石英闪长岩展开,锆石LA-ICP-MS U-Pb定年获得岩浆结晶年龄为(313.3±5.7)Ma,成岩时代为晚石炭世。花岗岩SiO_2含量58.13%~66.74%,具低CaO含量3.68%~5.79%和高Al_2O_3含量13.02%~13.68%特征。轻重稀土元素分馏明显,富集轻稀土元素,Eu弱正异常或无异常,δEu=0.95~1.3。岩石地球化学研究表明,花岗岩富集大离子亲石元素Ba,Sr,K和亏损高场强元素Nb,Ta,Ti,P,具火山弧花岗岩特征。结合岩石锆石LA-ICP-MS定年结果和区域地质背景,认为伊尔根布鲁克石英闪长岩可能是中天山南缘大洋俯冲消减作用的产物,该区大洋俯冲消减至少延续到晚石炭世。     

粤东新寮岽铜多金属矿区石英闪长岩锆石U-Pb年龄、地球化学及Hf同位素组成

新寮岽铜多金属矿是近年来在粤东地区新发现的一个铜矿床。对该矿床中与成矿关系密切的石英闪长岩进行了锆石U-Pb年龄、地球化学、Hf同位素研究,以约束其形成时代和岩石成因。测得石英闪长岩LA-ICP-MS锆石U-Pb年龄为161±1Ma(n=25,MSWD=0.57),被解释为岩体的成岩年龄。地球化学数据显示,石英闪长岩具有碱含量中等(Na2O+K2O=3.99%~5.05%),高镁(Mg O=4.53%~4.91%)的特征,属准铝质钙碱性系列。稀土和微量元素特征表明,其富集轻稀土元素和大离子亲石元素(K、Rb、Ba、Th、U),亏损重稀土元素和高场强元素(Nb、Ta、Ti、P),具弱负Eu异常(δEu=0.68~0.76)。电子探针分析结果表明,石英闪长岩中黑云母为镁质黑云母,具环带结构,斜长石为拉长石。锆石Hf同位素分析结果表明,石英闪长岩εHf(t)为-5.8~2.7,tDM2=1.03~1.58Ga。岩石地球化学和锆石Hf同位素组成特征表明,石英闪长岩源区较复杂,为壳幔混合源,可能为俯冲板片部分熔融并与楔形地幔橄榄岩相互作用形成,且岩浆上侵过程中有古老地壳物质的混染。综合岩石地球化学、矿物化学及Hf同位素特征,结合区域构造演化史和前人研究成果,推测岩体形成于俯冲背景下的活动大陆边缘环境。     

延边和龙地区闪长岩的年代学、地球化学特征及岩石成因研究

林省东部延边和龙地区中生代闪长岩的锆石 LA-ICP-MS U-Pb 年龄为 173~175 Ma。岩石的 SiO2 含量为 53.28%~58.02%, TiO2 含为 0.99%~1.08%,MgO 和 TFe2O3 含量分别为 1.96%~6.45% 和 6.59%~9.64%,Mg# 值为 37~59,Na2O 含量为 3.37%~4.88%, K2O 含量为 0.94%~2.30%,Na2O/K2O 为 1.70~4.16,Al2O3 含量为 15.87%~18.93%,相对富钠高铝,并且具有钠质钙碱性系列 向高钾钙碱性系列过渡的趋势,稀土元素球粒陨石标准化曲线显示其具有富含轻稀土元素(LREE)、贫重稀土元素(HREE) 以及无 Eu 负异常的特点。岩石富集大离子亲石元素(Rb,Th,Ba),明显亏损 Nb,Ta,Zr,Hf 和 Ti 等高场强元素 (HFSE)。 闪长岩的原始岩浆起源于受俯冲流体交代地幔楔的部分熔融,岩浆在上升过程中未受到明显的地壳混染。该期闪长岩形成 于与古太平洋板块俯冲相关联的活动大陆边缘环境。     

早侏罗世新特提斯洋俯冲作用——来自松多高镁闪长岩锆石U-Pb定年及Hf同位素的制约

冈底斯岩浆岩带中东部松多地区新发现的高镁闪长岩对于探讨青藏高原新特提斯俯冲演化历史具有重要意义。通过松多高镁闪长岩的LA-ICP-MS锆石U-Pb年龄、锆石Hf同位素和全岩地球化学组成的研究,表明松多闪长岩的锆石U-Pb年龄加权平均值为186.8±1.3Ma。该类岩石具有高硅、高镁的特点,Si O2含量为54.17%~58.81%,Mg O含量较高,介于6.26%~7.29%之间,Mg~#值介于64~67之间,Cr和Ni含量高。该岩石富集轻稀土元素,具有平滑右倾的稀土元素配分曲线及弱负Eu异常。富集Rb、Ba、Pb、K等大离子亲石元素,亏损Nb、Ta、Ti等高场强元素。锆石负εHf(t)值(-5~-14.3)及远大于其侵入年龄的古老Hf模式年龄(1543~2129Ma),揭示松多早侏罗世闪长岩经历了古老地壳物质的部分熔融。Sr/Y-Y和(La/Yb)N-YbN判别图解显示,其形成可能与赞岐岩的岩浆作用过程相似,形成于消减带之上的地幔楔环境。综合研究表明,松多地区在早侏罗世处于雅鲁藏布新特提斯洋板片向欧亚大陆俯冲的活动陆缘构造背景。     

青海省阳康地区晚奥陶世花岗岩地球化学特征及其地质意义

青海省阳康地区花岗岩岩石组合为细粒石英闪长岩、黑云母花岗闪长岩。通过对岩石地球化学分析发现,SiO_2含量为54.36%～70.16%,Al_2O_3含量为13.08%～17.01%,K_2O含量为1.57%～3.91%,Na_2O含量为2.37%～3.75%,CaO含量为1.91%～8.09%,里特曼指数σ为1.5～2.61,属偏铝质-过铝质钙碱性花岗岩;稀土总量(∑REE)为121.7×10~(-6)～458×10~(-6),LREE/HREE值为6.81～14.72,表现为轻稀土富集型,δEu值为0.46～1.16,Eu亏损明显,δCe略亏损;富集大离子亲石元素(Rb、Ba、K)和轻稀土元素(La、Ce、Nd),亏损重稀土元素(Yb、Lu)和高场强元素(Nb、Ta),具有明显的Eu和Sr、P、Ti的亏损。在石英闪长岩和花岗闪长岩中分别获得LA-ICP-MS锆石U-Pb年龄分别为(455.5±1.1)Ma和444Ma,形成时代为晚奥陶世。通过构造环境分析,认为阳康地区花岗岩是由挤压向拉伸环境转换的张驰阶段的岩浆侵位,属同造山花岗岩。     

北淮阳东段塘湾岩体地球化学特征、锆石U-Pb测年及地质意义

位于安徽北淮阳东段的塘湾岩体为凌家冲杂岩体的重要组成部分,岩石类型为石英闪长岩。该岩体偏铝质、低硅、富碱、高钠,属于高钾钙碱性系列岩石;稀土元素含量中等,（La/Yb）N与HREE/LREE值较高,重稀土相对亏损,Eu弱负异常,属轻稀土富集型;大离子亲石元素Rb、Ba、K、La、Nd富集,高场强元素Nb、Ta、Ti、P亏损。LA-ICP-MS锆石U-Pb测年结果显示塘湾岩体206Pb/238U年龄为（138.0±2.9）Ma,表明岩体为早白垩世岩浆活动的产物。基于区域地质背景及构造环境判别,塘湾石英闪长岩形成于后碰撞伸展构造环境。     

北山独龙包地区晚石炭世陆缘弧岩浆作用——花岗闪长岩锆石U Pb年龄及地球化学证据

本文报道了北山地区独龙包南花岗闪长岩的LA-ICP-MS锆石U-Pb年龄与全岩地球化学,以确定其形成时代、岩石成因及构造环境。花岗闪长岩中的锆石呈短柱状或近等轴粒状,具典型的振荡环带,Th/U值介于0.42~0.75之间,指示岩浆成因。对岩浆锆石的定年结果显示,独龙包南花岗闪长岩形成于303.4±2.1 Ma。该期花岗闪长岩的Si O2含量为63.73%~69.12%,Na_2O=3.69%~4.03%,K_2O=2.23%~2.73%,全碱(Na_2O+K_2O)为6.08%~6.44%,Al2O3含量较高(14.83%~15.89%),K2O/Na2O为0.58~0.74,A/NCK=0.91~0.99;该区花岗闪长岩富集轻稀土(LREEs)和大离子亲石元素(LILE)Rb、Th、U、Pb,亏损重稀土元素(HREEs)和高场强元素(HFSE)Nb、Ta、P、Ti,且轻重稀土元素分馏较强,(La/Yb)N变化于4.77~6.35,具有弱的负铕异常,δEu为0.79~0.94。上述特征表明,该期花岗闪长岩属于准铝质钙碱性I型花岗岩,岩浆源区为下地壳,受到地幔物质的混染,形成构造背景为陆缘弧。结合邻区特征,得出红石山—百合山—蓬勃山蛇绿岩带代表的洋盆于晚石炭世可能发生了南北双向俯冲。     

粤北扶溪岩体成因及时代:来自矿物化学、岩石地球化学及LA-ICP-MS锆石U-Pb年龄证据

分析了粤北扶溪地区花岗闪长岩角闪石、黑云母矿物化学组成,全岩岩石地球化学及LA-ICP-MS锆石U-Pb年龄。结果显示,花岗闪长岩中角闪石属镁角闪石,黑云母属镁质黑云母。岩石硅含量较高,w(SiO_2)为63.86%~66.19%;富碱,w(K_2O)为4.07%~4.71%,w(Na_2O)在2.42%~2.76%;铝质量分数中等,w(Al_2O_3)为14.27%~15.02%。稀土元素总量w(ΣREE)为183.22×10~(-6)~283.31×10~(-6),稀土元素配分模式右倾,中等强度负Eu异常(0.62~0.80),富集Rb、K、Th、Sr、Pb、Nd等大离子亲石元素,亏损Th、U、Zr、Hf、Nb、Ta、Ti等高场强元素。LA-ICP-MS锆石U-Pb年龄为(440.7±3.3)Ma(MSWD=2.4,n=18)。上述分析结果表明花岗闪长岩为I型花岗岩,是早志留世岩浆活动产物,岩浆主要来源于地壳物质的部分熔融,在温度777~802℃、压力316~442 MPa和氧逸度约lgf(O_2)=-14条件下侵位结晶。     

新疆中天山巴仑台闪长岩成因及其地质意义

巴仑台闪长岩反映的大洋俯冲信息为对比乌瓦门蛇绿岩与西侧长阿吾子和东侧库米什蛇绿岩的关系,探讨南天山洋的洋-陆演化过程具有重要意义。闪长岩具高碱和高铝特征,(Na2O+K2O)=4.14%~7.05%,Al2O3为14.62%~17.35%,为一套高钾钙碱性系列岩石,(La/Yb)N平均10.46,以富集轻稀土元素和大离子亲石元素(如K、Rb、Ba、Pb等)、亏损Nb、Ta、Ti等高场强元素为特征,形成于岛弧环境。闪长岩LA-ICP-MS锆石U-Pb年龄为(430.1±1.1)Ma,锆石εHf(t)=-12.7~-7.6,二阶段Hf模式年龄TDM2为1895~2219 Ma,指示巴仑台闪长岩为早志留世南天山洋北向俯冲,导致中天山古老结晶基底部分熔融形成。     

Wavelength-dispersive X-ray fluorescence spectrometric determination of Sc, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Ba, Pb, and Th in komatiites

Komatiites are mantle-derived ultramafic volcanic rocks. Komatiites have been discovered in several States of India, notably in Karnataka. Studies on the distribution of trace-elements in the komatiites of India are very few. This paper proposes a simple, accurate, precise, rapid, and non-destructive wavelength-dispersive x-ray fluorescence (WDXRF) spectrometric technique for determining Sc, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Ba, Pb, and Th in komatiites, and discusses the accuracy, precision, limits of detection, x-ray spectral-line interferences, inter-element effects, speed, advantages, and limitations of the technique. The accuracy of the technique is excellent (within 3%) for Sc, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Zr, Nb, Ba, Pb, and Th and very good (within 4%) for Y. The precision is also excellent (within 3%) for Sc, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Ba, Pb, and Th. The limits of detection are: 1 ppm for Sc and V; 2 ppm for Cr, Co, and Ni; 3 ppm for Cu, Zn, Rb, and Sr; 4 ppm for Y and Zr; 6 ppm for Nb; 10 ppm for Ba; 13 ppm for Pb; and 14 ppm for Th. The time taken for determining Sc, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Ba, Pb, and Th in a batch of 24 samples of komatiites, for a replication of four analyses per sample, by one operator, using a manual WDXRF spectrometer, is only 60 hours.     

高压微波消解法测定醋酸纤维过滤器采集的微尘粒子中的砷镉钴铬铜铁锰镍铅钒锌

最新的流行病学研究表明,空气中较高浓度的悬浮细颗粒可能对人类的健康有不利的影响。根据该项研究显示,由于心脏病、慢性呼吸问题和肺功能指标恶化而导致死亡率的升高与细尘粒子有关。这些研究结果已经促使欧盟于1999年4月出台了限制空气中二氧化硫、二氧化氮、氧化氮、铅和颗粒物含量的法案(1999/30/EC),对各项指标包括对可吸入PM10颗粒的浓度提出了新的限制性指标。PM10颗粒是指可以通过预分级器分离采集的气体动力学直径小于10μm的细颗粒。目前研究的兴趣重点逐步偏向PM2.5这些更细微颗粒物,PM2.5这种颗粒物对健康有明显的不利影响。在欧盟指令2008/50/EC中,对PM10和PM2.5都提     

硅酸盐类样品中硅、铁、铝、钛、锰、钙、镁、钾、钠和磷的x射线荧光光谱测定

本文拟定了一种以熔融法制备样片,用X射线荧光光谱测定硅酸盐类样品中Si、Fe、Al、Tj、Mn、Ca、Mg、K、Na、P等元素的分析方法。在对不同靶材X光管和分光晶体实验对比的基础上,选择了最佳的测量条件。该法具有快速、准确,测量范围广,检测限低,价格便宜等优点。经过近百个各种类型标样或管理样品的分析对比表明,本法不仅适用于硅酸盐类岩石样品的分析,还适用于铁矿、铝土矿、碳酸盐类岩矿样品以及水泥、耐火材料等样品的分析。     

Isotopic systematics of He,Ar, S,Cu, Ni,Re, Os,Pb, U,Sm, Nd,Rb, Sr,Lu, and Hf in the rocks and ores of the Norilsk deposits

This paper reports the first results of a study of 11 isotope systems (³He/⁴He, ⁴⁰Ar/³⁶Ar, ³⁴S/³²S, ⁶⁵Cu/⁶³Cu, ⁶²Ni/⁶⁰Ni, ⁸⁷Sr/⁸⁶Sr, ¹⁴³Nd/¹⁴⁴Nd, ^206–208Pb/²⁰⁴Pb, Hf–Nd, U–Pb, and Re–Os) in the rocks and ores of the Cu–Ni–PGE deposits of the Norilsk ore district. Almost all the results were obtained at the Center of Isotopic Research of the Karpinskii All-Russia Research Institute of Geology. The use of a number of independent genetic isotopic signatures and comprehensive isotopic knowledge provided a methodic basis for the interpretation of approximately 5000 isotopic analyses of various elements. The presence of materials from two sources, crust and mantle, was detected in the composition of the rocks and ores. The contribution of the crustal source is especially significant in the paleofluids (gas–liquid microinclusions) of the ore-forming medium. Crustal solutions were probably a transport medium during ore formation. Air argon is dominant in the ores, which indicates a connection between the paleofluids and the atmosphere. This suggests intense groundwater circulation during the crystallization of ore minerals. The age of the rocks and ores of the Norilsk deposits was determined. The stage of orebody formation is restricted to a narrow age interval of 250 ± 10 Ma. An isotopic criterion was proposed for the ore-bearing potential of mafic intrusions in the Norilsk–Taimyr region. It includes several interrelated isotopic ratios of various elements: He, Ar, S, and others.     

Viscous, cohesive, non-Newtonian, depositing, radial slurry flow

Mining induced subsidence can significantly affect mining costs where major surface facilities and natural environment need to be protected. Overburden grout injection is a technology used to control coal mine subsidence by injecting the mine waste material extracted from the coal back into the inter-burden rock during longwall mining. The flowing slurry is here categorised as a nonlinear viscous cohesive (Bingham plastic) fluid. During longwall mining the grout slurry is pumped into the separated beds of the rock mass through a central vertical borehole, which is drilled deep into the inter-burden rock strata above the coal seam. However, a blockage can occur in the injection system when the slurry velocity falls below a certain critical threshold velocity, indicating a material phase change from cohesive-viscous to cohesive-frictional. In situ field injection tests through boreholes have been simulated at a smaller scale at the CSIRO laboratory in Brisbane by pumping the slurry through a radial disk (gap = 4 mm) from its centre. Laboratory experiments indicate a general, nonlinear, cohesive, viscous, frictional model for shear behaviour of the slurry, in which the material shear parameters are functions of the disk radial distance. Complete dimensional and dimensionless analytical solutions have been developed based on an approach related to Bingham–Herschel–Bulkley fluid mechanics. The derived formulae include relations for minimum pump pressure, local pressure and pressure gradient, wall shear stress, volume rate, velocity and velocity gradient. The theoretical results match the experimental measurements. The experiments covered slurries with maximum particle sizes of 0.5 to 2 mm with about 50% being larger than 100 µm. The viscosities at the various solids concentrations were measured with a standard torsion viscometer. This study differs from the previous research in several distinct aspects, namely, consideration of the variable shear parameters rather than fixed values, inclusion of total nonlinear behaviour, and implementation of a friction function to mimic behaviour of the deposited and consolidating stiff slurry, which can cause a significant pressure rise as a result of the increased shear resistance.     

硅酸盐中铁、锰、钛、钙、钾、磷、硅、铝、镁、钠、锶、铷、钡的X-射线荧光光谱定量测定

本文介绍样品经四硼酸锂熔融制成玻璃小饼。采用Lachance模式和理论a系数来校正元素间的效应,由3080E型X-射线荧光谱仪和DF-350B数据处理系统完成硅酸盐中十三个项目的测定。     

Bellechester,Minnesota, USA,lagoon collapses

Bellechester, Minnesota, is a small community of approximately 155 residents located on the county line between Goodhue and Wabasha counties in southeast Minnesota's karst region. Bellechester is served by a 21-year-old wastewater treatment facility (WWTF) consisting of three waste-stabilization ponds. On 28 April 1992 six sinkholes were discovered to have drained cell 2 of the WWTF resulting in the loss of approximately 8.7×10⁶ 1 of partially treated effluent and about 600 m³ of soil into previously undetected subsurface voids of unknown dimensions. In the week following the collapse, approximately 200 water wells located within a 5-km radius of the WWTF were sampled in an after-the-fact, emergency sampling program. Twelve samples with elevated fecal coliform levels, 18 samples with nitrate-nitrogen greater than the 10 mg/1 standard, and no samples with elevated chlorides were found. However, the elevated levels could not be unambiguously attributed to the WWTF collapse. This is the third WWTF to fail by sinkhole collapse in southeast Minnesota since 1974. All three collapsed lagoons have been located in similar geomorphic and stratigraphic settings. However, at least two lagoons have collapsed in the adjacent area in northeast Iowa, and these lagoons are located at different stratigraphic positions. Twenty-two WWTFs constructed in southeast Minnesota's karst region in the last 25 years have been identified as subject to potential sinkhole collapse. An unknown but significant number of manure storage lagoons, flood control structures, etc., have also been constructed in the karst region and are at risk. Public agencies are beginning to develop plans to deal with the risk associated with existing and future waste lagoons in this environment. The critical hydrogeologic parameters that can be used to prioritize the risk of collapse at existing facilities include: (1) the lithology of the first bedrock beneath each lagoon, (2) the thickness of surficial materials between the lagoon and the bedrock surface, (3) the presence and construction of liners (seepage rate), and (4) the proximity to existing sinkholes.     

Mercury,arsenic, antimony,and selenium contents of sediment from the Kuskokwim River,Bethel, Alaska,USA

The Kuskokwim River at Bethel, Alaska, drains a major mercury-antimony metallogenic province in its upper reaches and tributaries. Bethel (population 4000) is situated on the Kuskokwim floodplain and also draws its water supply from wells located in river-deposited sediment. A boring through overbank and floodplain sediment has provided material to establish a baseline datum for sediment-hosted heavy metals. Mercury (total), arsenic, antimony, and selenium contents were determined; aluminum was also determined and used as normalizing factor. The contents of the heavy metals were relatively constant with depth and do not reflect any potential enrichment from upstream contaminant sources.     

滇东南花岗岩与锡、银、铜、铅、锌多金属矿床的成因关系

滇东南锡、银、铅、锌多金属矿床主要分布在个旧、白牛厂、都龙3个矿区,而滇东南较大的3个花岗岩体又分别出露在3个矿区或附近.花岗岩体均形成于燕山晚期,岩石化学、矿物成分相似,富含锡、银、铅、锌、钨、铜等成矿元素.矿床主金属元素组合与岩体之间的距离由远而近出现由锡、钨、(铍、铌、钽)→锡、钨、(铁)、铜、铟→锡、铅、锌、银、铟、(锑)有规律的变化.花岗岩浆是成矿物质来源和成矿热源.岩浆侵入初期使上覆地层隆起产生背斜(凹陷部位成向斜);同时使地层产生一系列裂隙、压性断层或层间断裂;岩浆侵入晚期,这些断层再次活动,表现为张性,岩浆产生的含矿热液沿由其活动所造成的断裂迁移、充填、交代、沉淀而形成矿床.     

岩石密度和超高压岩石折返速率

在常温常压条件下对中国大陆科学钻CCSD主孔100-3000米岩心样品进行了密度测量,建立了密度连续剖面,并界定了不同超高压岩石的密度值。通过对比高温高压物性实验资料,岩石密度随着退变程度增强而降低,榴辉岩密度变化序列为3.52g/cm3→3.49g/cm3→3.07g/cm3→2.93g/cm3。超高压长英质岩石密度变化序列为3.00g/cm→2.80g/cm3→2.65g/cm3。上述实验资料是讨论不同折返阶段岩石所受浮力的基础,为研究折返速率大小提供了基本参数。本文通过折返板块运动平衡时,上浮力与粘滞力平衡这一关系式,定量研究了大陆俯冲板块的折返速率,认为密度差产生上浮力从而引起折返,温度对板块折返速率的影响最为显著;密度差大小、折返角度、折返板块大小对折返速率也有直接的影响。定量模拟分析表明,在温度高于850℃时,板块的折返速率可以超过100mm/a;当温度降至700℃时,折返速率则低于1.5mm/a。作者认为在折返早期,温度较高,板块快速折返至60-70km榴辉岩相深度;随着传导散热,温度降低,板块以较慢的速率折返至中下地壳。折返速率的估算表明,浮力是板块折返第一阶段(从>100km深部折返至<40km的中下地壳)的主要驱动力。