Montelli et al. (2004) Science
13
Plume
Plate
板 块 构 造 与 地 幔 柱 之 间 的 关 系
14
Relationship between Plate subduction and Plume initiation
15
地球系统科学
板块构造与地幔柱
T P
XH2O
Zheng et al. (2004) GCA
49
水岩反应
ZhenHale Waihona Puke et al. (2003) ESR
50
地幔超柱活动与花岗岩浆作用
(Chemical Geodynamics)
初期：地幔热能为主，在拉张型增生造 山带引起表壳物质熔融和中低温热液蚀 变，形成S型花岗岩(初生地壳Nd-Sr同位 素特点) 峰期：地幔物质为主，在大陆边缘裂谷 构造带引起初生地壳重熔和高温地表水岩反应，形成I型花岗岩(M亚型)
X X X X X X X X XX
40
ca.825Ma花岗岩源区
41
1.1 to 0.9 Ga
0.83 to 0.74 Ga
Grenvillian subduction Mantle superplume
42
ca.820Ma花岗岩浆作用
Plume head effect ?
43
Rodinian Breakup? Bimodal magmatism?
d18O (%0) Zircon
32
Single-stage Hf Model Age
(Bimodal Igneous rocks of ca.750 to 760 Ma)
1400
Any meaning?
1200
(a)
TDM (Ma)
1.07 0.09 Ga
1000
Mean = 1071±92 Ma MSWD = 9.2
11
Three-dimensional view of deep mantle in tomographical model
Montelli et al. (2004) Science 12
Three-dimensional view of the shallow mantle and the newly discovered plumes in vertical model
45
裂谷构造带
破火山口 垮塌
热液蚀变
低18O岩浆活动
地幔柱
46
大陆边缘 岩浆活动
物质： ~800 Ma 初生地壳 热能： ~750 Ma 地幔超柱 背景： 主动裂谷 构造带
47
ca.750Ma花岗岩浆作用
Plume head effect ?
48
扬子板块北缘新元古代岩浆活动
锆石U-Pb年龄主要集中在700~800Ma， 岩浆活动峰期约在750Ma。 锆石氧同位素比值范围-11‰ ~ +9‰， 大多数锆石d18O 值低于地幔锆石值，大 约一半为负d18O 值。 新元古代高温热液蚀变，蚀变岩石部分 熔融形成低d18O 岩浆。 与超大陆裂解和地幔超柱事件有关
Bimodal compositions of both chemistry and isotope
35
Timing of Crust-Mantle Interaction
Initial phase:
Heat: Crustal remelting at ~820 Ma
Peak phase:
Mass: Rift magmatism at ~750 Ma Progressive addition of mantle-derived material to the crust
892±12 Ma Depleted Mantle
Hf(t)
8 4 0 -4 -8 0
89212 Ma
CHUR
400
800
1200
1600
2000
39
Hf Model Age (Ma)
Mass transfer of mantle to crust at ~900 Ma by Arc magmatism
Paleoproterozoic to Archean basements
Meteoric-hydrothermal alteration
地 幔 柱
新元古代
扬子板块北缘岩浆活动和热液蚀变
44
加厚地壳 部分熔融
物质： ~900 Ma 大陆弧 热能： ~825 Ma 地幔柱 背景： 拉张增生 型造山带
Predictions of plume Narrow, vertical seismic structures traversing the whole mantle High temperatures Relative fixity of hotspots Age progression of volcanic chain
787±18 Ma
Hf(t)
8 4 0 -4 -8 0
78718 Ma
CHUR
400
800
1200
1600
2000
38
Hf Model Age (Ma)
Age of Juvenile Crust
Leucogranite at Sanfang
20
98GX9-1
16 12
Arc magmatism?
5
新元古代早期扬子板块周边
Zhou MF et al. (2002) EPSL
Zhou JC et al. (2004) Wang XL et al. (2004)
Arc genesis?
6
Episodic Growth of Juvenile Crust
Subduction zone: Arc Magmatism Mantle plume: Oceanic Plateau Rift magmatism
-2 2 4 6 8 10 12
d18O ( ) Zircon
31
Mineral O Isotopes (2)
4
18 D O (%0) Plagioclase-Zircon
(b)
2
Equilibrium Equilibrium
0
-2
Guangxi Yunnan Sichuan
-4 2 4 6 8 10 12
“阴”与“阳”
(Anderson, 2004)
16
在地球科学中的空间尺度
微观分析 vs. 宏观构造
17
华南新元古代岩浆岩
X X X XX X
18
810~830 Ma: S-type
华南 新元古代 岩浆岩
750~760 Ma: I-type
19
华南新元古代岩浆岩
20
华南新元古代花岗岩
锆石Hf和O同位素地球化学 阴极发光(CL)结构照相 MC-ICP-MS Lu-Hf同位素分析
Red: core-mantle boundary, yellow: transition zone, green-lithosphere 10 (Courtillot et al., 2003, EPSL)
DEBATE Plume vs Non-plumes
(Science, 2003, May 9)
=
Observations
Shallow thermal anomaly at classic hotspots Hotspot is not so hot Hotspot is not fixed, Not all volcanic chain has age progression
7
Uplift of mantle plume is evidenced by a rapid, pre-volcanic uplift
8
地幔柱与地幔超柱
浅柱 White & KcKenzie (1989)
Campbell & Griffiths (1990)
深柱
9
Hotspots around the world
901±20 Ma
Mean = 901±20 Ma MSWD = 0.68
1
0 600 700 800 900 1000 1100
TJC (Ma)
37
Age of Juvenile Crust
Gabbro at Shaba
20
98KD111
16 12
Plume magmatism?
Depleted Mantle
800
33
Two-stage Hf Model age
(Granitoids of ca.825 Ma)
2300
Paleoproterozoic basement? (b)
2100
(Ma) T
c DM
1900
1.860.07 Ga
1700
Mean = 1863±69 Ma MSWD = 1.3
1500
28
Zircon Hf-O Isotopes (1)
12
(a)
10
18 d O (%o)
8
6
Guangxi
4
Yunnan Sichuan
2 -8 -4 0 4 8 12
Hf(t)
29
Zircon Hf-O Isotopes (2)
12
(b)
10
18 d O (%o)
8
6
Guangxi
4
Yunnan Sichuan
华南新元古代花岗岩锆石Hf和O 同位素地球化学: 地幔柱头效应?