the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 27 Aug 2024
Tectonic interplay between the South Tibetan Detachment System and the North Himalayan genesis dome
Abstract. The formation and evolution of the Himalayas are intimately linked to the South Tibetan Detachment System (STDS) in the northern Himalayas. Despite ongoing controversies about the deep structural style of the STDS, understanding the emplacement mechanism of the leucogranite in the North Himalayan gneiss domes (NHGDs) remains challenging due to insufficient information about deep structures. In this study, we characterized the subsurface structure of the STDS on the eastern side of the Tethys Himalayas and analyze the relationship between STDS tectonic activity and the formation of the NHGD. We conducted a deep seismic reflection survey with a line length of over 135 km and performed geological field investigations in the eastern Tethys Himalayas (92° E) from 2017 to 2018. Our findings indicate that the STDS presents as a roof thrust fault of duplex structures in the eastern Tethys Himalayas and displays characteristics of two-phase denudation (STDS-1 and STDS-2) from the Miocene, corresponding to the two-phase Tethys tectonic uplift. The first phase of denudation (STDS-1) led to the exposure of its structure around the Yarlhashampo dome. Both STDS-1 and STDS-2 denudation activities play crucial roles in promoting the partial melting of middle crust metasediments, which subsequently migrated upward to form leucogranite through diapirism in the core of the Yarlhashampo dome.
- Preprint
(2474 KB) - Metadata XML
- BibTeX
- EndNote
Status: closed
-
RC1: 'Comment on egusphere-2024-2468', Anonymous Referee #1, 25 Sep 2024
The manuscript "Tectonic interplay between the South Tibetan Detachment System and the North Himalayan genesis dome" by Xinyu Dong et al. analyzes the deep structures of the southern Tibetan detachment system and its relationship with the Yarlhashampo dome. The data used for the study are a normal incidence profile directly traversing the major structures in the eastern segment of the gneiss dome belt. The newly acquired resulting seismic section provides a detailed picture of the crust.
From the interpreted section, the authors deduce the crustal deformation styles from the shallow to the depth, then analyze the evolution of the southern Tibetan detachment system and how the relative dome structure and granites formed. The data are of good quality, and the analysis is adequate. The results are well presented, although some improvements are suggested. The manuscript is well organized for the most part, but some parts should be rewritten. In my opinion, it is suitable for publication after some major modifications. Some issues need to be resolved before the manuscript can be accepted for publication. My comments and suggestions are listed below.
Abstract：
Line 24: What does “its” mean? Do you mean the STDS? Using the project directly will be better.
Lines 25-27: In lines 17-18, “analyze the relationship between … and the formation of the NHGD,” so I suppose you should highlight the formation mechanism of the NHGD at the end of your abstract.
Geological Background:
If you state the geological background in some kind of order, please add the statement in the first paragraph of this section to help readers follow.
Line 73-74: Please add a reference for the statement “this zone is composed of …”.
Line 80: “bound” should be “bounded”
Line 136: “Its root connect(s) to the STDS on the south side” based on surface geological observations or? Please add supporting methods or materials, since your work is revealing the detailed structures of the STDS in depth.
Line 138: “Lhozhag fault” in the text but “Lhozhag thrust” in Fig. 2. Making statements consistent and adding figure information is suggested.
Line 188: The boundary between the lower and middle structure layer of gneiss domes is debated. How to analyze whether the detachment fault is part of the STDS or not based on geological observations?
Line 211: You divide the profile into three parts, south, central and north parts based on what criteria? Please add some statements before 3.3.1.
Line 218: What does “CMP” mean? To make it easier for readers to follow your text, please also note the geophone interval (like 25 m) in the 3.2 seismic reflection data part and add distance marks in Fig. 4.
Line 222: “in the fault’s hanging wall and footwall” should be “in the hanging wall and footwall of the fault”.
Line 228: You didn’t mention Lhunze fault in 3.3.1 section, why? I think this structure also belongs to the southern part of this profile.
Line 235: I suggest changing the expression of “comprises three layers: …” to “comprised three parts: the upper, middle, and lower layers”.
Line 242: The reflection numbered by 3 is a north-dipping strcuture in the profile as I can see, why do you use “subhorizontal”?
Discussion:
Line 420-421 : What do you mean “due to footwall decompression melting caused by the gravity collapse of STDS-1”? If the gravity collapse of STDS-1 is the reason for the decompression melting in the footwall, why did the STDS experience gravity collapse? If duplexing is the reason, then both of the decompression melting and the gravity collapse should be the results.
Line 422: Lhozhag fault is a southward thrusting fault.
Line 430: What do you mean by “the Lhozhag fault ahs extended in the N-S direction”, since this fault is a E-W striking fault.
Line 449-541: Do the high Sr/Y and high Na/K mica granites differ from leucogranites? Since this kind of granite seems to have formed from the Indian lower crustal mafic rocks caused by extra heating from the asthenosphere, but you also metioned decompresion melting in Line 420. Could you explain this to reduce the confusion?
Line 466: What does “This” mean? The duplex thickening or the gravity collapse, since these two factors indicate two different melting mechanism?
Line 468-470: “This melts migrated upward, diapirically reforming the STDS-1 and resulting in the formaiton of the … dome…”. This sentence expresses that the migration the melting caused the dome structure. Am I right? But in the Conclusion part, “the activity of the Lhozhag fault and STDS contributed to the formation of the … dome” expresses a different opinion. Expressions should be considered carefully.
Figures:
Fig. 05 Please move the elevation figure in Fig. 5b to the Fig.5a, so that readers can easily match the CMP numbers with the fault marks.
Citation: https://doi.org/10.5194/egusphere-2024-2468-RC1 -
RC2: 'Comment on egusphere-2024-2468', Anonymous Referee #2, 29 Sep 2024
The paper by Dong et al. presents data regarding the tectonic activity of the South Tibetan Detachment System in relation with the evolution of the North Himalayan Gneiss domes.
They present deep seismic reflection data to interpret the deep structure of the South Tibetan Detachment System and try to discuss its role in the partial melting process that gives rize to the leucogranite in the core of the dome.
This is an interesting topic for the scientific community by the way in my opinion the paper is not suitable for publication in the present form. It presents many issues that should be better explained and clarified. The text is not fluent, english should be strongly revised and very often the geological teminology is not right. In my opinion the conlusions are not well supported by the presented data and the authors need to collect many more structural data to support their conclusion.
Sometimes data and interpretation are mixed together.
The AA do not take in account many published papers , they have to implement the references in the text.
Figures are necessary but some of them need some main modifications
One major problem is that there is , throughout the text, a misunderstanding between “uplift” and “exhumation”. The AA need to speak about exhumation and they have to discuss their data in the frame of all the proposed tectonic models and not only discuss two of them. So they have to implement this part of the discussion and consider a wider range of tectonic models. The discussion should be amplified, if the Authors want to discuss the tectonic models proposed for the exhumation of the metamorphic core of the belt they need to improve it a lot as they missed some main proposed models (i.e. “Channel flow”, “In sequence shearing”).
Another important issue is that it is necessary to document and discuss the evolution of the STDS from contractional to extensional tectonic settings. They refer to paper by Chen et al. 2018 in the area of the Yarlhashampo dome to testify the switch between compression and extension. This is not true as Chen et al. (2018 ) recognized a lower and an upper STDS but both of them show extensional kinematic indicators, so AA must pay attention to the reference and if they have data that support this tectonic switching they have to present them.
For which concerns the Kalopani shear zone (line414), that AA interpreta s a branch of the STDS, it is well established that it is located in the GHS and it is not a branch of the detachment (i.e. between GHS and THS), but it is a top-to-the-South ductile tectonometamorphic discontinuity (sensu Montomoli et al., 2013) responsible for the beginning of the exhumation of the GHS (Carosi et al., 2016)
In addition as the Lhozang fault covers a key role in the proposed tectonic model it is necessary to describe it, its kinematic indicators and related structural elements. This has never been done all along the text
In the “Geological Background” it is mandatory to introduce the geological setting of the study dome.
Introduction
In this paragraph when you describe the different possible interpretations about the origin of the STDS you have also to consider the STDS as a “stretching fault”.
Please add also some more fundamental references about the STDS just to suggest tha most important but there are much more : Searle 1998, Carosi et al., 1998, Waters 2019,Law et al., 2004.
Line 49 Add Wang et al
Line 64 Delete “relevant”
Geological background
The first paragraph of this chapter needs to be completely rephrased. The “extintion” of an oceani s not the right term (Line 71), you can substitute with “closing”. For the main architecture of the study area you have from North to South the southern margin of the Asian Plate, the suture but not the Himalayan orogen as you wrote bit the northern margin of the Indian plate. There isconfusion also in the lines 74-75, please rewrite
Lines 77: Common terminology used by the himalayan scientific community for the main tectonic units building up the belt are:
-Tethyan Himalayan Sequence
- Greater Himalayan Sequence
-Lesser Himalayan Sequence
For the main tectonic discontinuities use the following terminology:
Main Central Thrust delete “fault”
Main Frontal Thrust not Main Front Thrust (Line 83)
Please use the above terminology through all the text .
(Line 85) The active age makes no sense use “age of activity”
Lines 104- 106 Regarding the THS it is not a sub-unit but it is a main tectonic unit building up the belt. The description of the Unit is not clear. At first describe the stratigraphic sequence (see for example Antolin et a 2011 , Dunkl et al 2011) then you can describe the tectonic evolution (see Montomoli et al. 2017, Aikman et al., 2008).
Line110-113: I suggest to delete this sentence as it is not usefull for your paper
Lines 115-116: check that all these faults are represented in the geological map of figure 2 and please use the same names.
Lines 118-119 Delete this sentence. It makes no sense to introduce the local name of the STDS for the western part of the belt. It has many local names across the chain so that it is not necessary to introduce them all.
Lines 124 Add Visonà et al., 2012 (Lithos), Searle 2010.
Line133: This fault THRUSTS some indian….
Line 144 Please give some data regarding the activity of the Rongbu-Gudui fault or refer to literature
Line 155 Substitute “expansion” with “extention”
Lines 163-168 Rewrite this paragraph. Plese have a look to Carosi et al . 2019 Geol. Soc. of London. You need to better describe the GHS. What does it mean that the GHS experienced “magmatic extrusion?”. Parametamorphic rocks, what are they ? Do you mean they are metamorphic rocks from a sedimentary protolith? (“metamorphic rocks and parametamorphic rocks” ??)
Results
Line 175 You never described the “sinistral thrust fault encircling the dome” . You need to introduce the geological setting of the dome. This paragraph is very confusing and I cannot understand which kind of rocks crop out and which is the general architecture of the STDS. In addition figure 3 is not clear. Please refer to paper of Chen et al (2018).
In figure 3B you draw an unconformity. Are you sure this is a primary boundary? Is it not a shear zone?
Line 187: I disagree. Boudins structures not always testify extensional tectonics, they can develop also in a contractional tectonic setting
Lines 275-287 Put this paragraph in the DISCUSSION, here you are presenting your results
Lines 393. This is not uplift but extrusion! You have to discuss all the proposed tectonic models not only these two. See Montomoli et al. 2013 for a review of the tectonic models. See Carosi et al. 2018, 2019, for the “In sequence shearing model” and Kohn 2008 for the “wedge model”.
Figure 1. Some main problems arise from this figure. The AA put the YZSZ inside the THS in central Tibet. This is not the case, if the AA have some data they have to discuss them, anyway the YZSZ is the relict of the Tethyan ocean and it is located between the Indian derived units and the Gandgese batholit. There i salso a Klippen of GHS over the THS in NW part, is i true? Please put some geographic references in the figure
Figure 2 The geological map presents many problems. One main problem regards the legend that should be constructed dividing the different tectonic units (i.e. GHS, THS…) For each unit you should present the different lithostratigraphic unit ordered from the youngest to the oldest. Now it is a completely mess and you mixed all the things.
In addition:
Line 752 I suggest to avoid “eclogite strata”
Line755 What do you mean with “Ophiolite in Creatceous”?
Line758 Spelling “Reverse faut”
Line 759 Are you sure you have gneissic foliation in acid intrusive bodies (see NE of Gonggai)?
Line 760 THS not present in the map
Line 761 YLSP not present in the figure
Yellow field between GT and GCT not present in the legend
Many acronymouses present in the map are not described in the legend (i.e. Pt2-3; K1; J3K1; Tr3…) In the legend everything appearing in the map should be explained
Citation: https://doi.org/10.5194/egusphere-2024-2468-RC2
Status: closed
-
RC1: 'Comment on egusphere-2024-2468', Anonymous Referee #1, 25 Sep 2024
The manuscript "Tectonic interplay between the South Tibetan Detachment System and the North Himalayan genesis dome" by Xinyu Dong et al. analyzes the deep structures of the southern Tibetan detachment system and its relationship with the Yarlhashampo dome. The data used for the study are a normal incidence profile directly traversing the major structures in the eastern segment of the gneiss dome belt. The newly acquired resulting seismic section provides a detailed picture of the crust.
From the interpreted section, the authors deduce the crustal deformation styles from the shallow to the depth, then analyze the evolution of the southern Tibetan detachment system and how the relative dome structure and granites formed. The data are of good quality, and the analysis is adequate. The results are well presented, although some improvements are suggested. The manuscript is well organized for the most part, but some parts should be rewritten. In my opinion, it is suitable for publication after some major modifications. Some issues need to be resolved before the manuscript can be accepted for publication. My comments and suggestions are listed below.
Abstract：
Line 24: What does “its” mean? Do you mean the STDS? Using the project directly will be better.
Lines 25-27: In lines 17-18, “analyze the relationship between … and the formation of the NHGD,” so I suppose you should highlight the formation mechanism of the NHGD at the end of your abstract.
Geological Background:
If you state the geological background in some kind of order, please add the statement in the first paragraph of this section to help readers follow.
Line 73-74: Please add a reference for the statement “this zone is composed of …”.
Line 80: “bound” should be “bounded”
Line 136: “Its root connect(s) to the STDS on the south side” based on surface geological observations or? Please add supporting methods or materials, since your work is revealing the detailed structures of the STDS in depth.
Line 138: “Lhozhag fault” in the text but “Lhozhag thrust” in Fig. 2. Making statements consistent and adding figure information is suggested.
Line 188: The boundary between the lower and middle structure layer of gneiss domes is debated. How to analyze whether the detachment fault is part of the STDS or not based on geological observations?
Line 211: You divide the profile into three parts, south, central and north parts based on what criteria? Please add some statements before 3.3.1.
Line 218: What does “CMP” mean? To make it easier for readers to follow your text, please also note the geophone interval (like 25 m) in the 3.2 seismic reflection data part and add distance marks in Fig. 4.
Line 222: “in the fault’s hanging wall and footwall” should be “in the hanging wall and footwall of the fault”.
Line 228: You didn’t mention Lhunze fault in 3.3.1 section, why? I think this structure also belongs to the southern part of this profile.
Line 235: I suggest changing the expression of “comprises three layers: …” to “comprised three parts: the upper, middle, and lower layers”.
Line 242: The reflection numbered by 3 is a north-dipping strcuture in the profile as I can see, why do you use “subhorizontal”?
Discussion:
Line 420-421 : What do you mean “due to footwall decompression melting caused by the gravity collapse of STDS-1”? If the gravity collapse of STDS-1 is the reason for the decompression melting in the footwall, why did the STDS experience gravity collapse? If duplexing is the reason, then both of the decompression melting and the gravity collapse should be the results.
Line 422: Lhozhag fault is a southward thrusting fault.
Line 430: What do you mean by “the Lhozhag fault ahs extended in the N-S direction”, since this fault is a E-W striking fault.
Line 449-541: Do the high Sr/Y and high Na/K mica granites differ from leucogranites? Since this kind of granite seems to have formed from the Indian lower crustal mafic rocks caused by extra heating from the asthenosphere, but you also metioned decompresion melting in Line 420. Could you explain this to reduce the confusion?
Line 466: What does “This” mean? The duplex thickening or the gravity collapse, since these two factors indicate two different melting mechanism?
Line 468-470: “This melts migrated upward, diapirically reforming the STDS-1 and resulting in the formaiton of the … dome…”. This sentence expresses that the migration the melting caused the dome structure. Am I right? But in the Conclusion part, “the activity of the Lhozhag fault and STDS contributed to the formation of the … dome” expresses a different opinion. Expressions should be considered carefully.
Figures:
Fig. 05 Please move the elevation figure in Fig. 5b to the Fig.5a, so that readers can easily match the CMP numbers with the fault marks.
Citation: https://doi.org/10.5194/egusphere-2024-2468-RC1 -
RC2: 'Comment on egusphere-2024-2468', Anonymous Referee #2, 29 Sep 2024
The paper by Dong et al. presents data regarding the tectonic activity of the South Tibetan Detachment System in relation with the evolution of the North Himalayan Gneiss domes.
They present deep seismic reflection data to interpret the deep structure of the South Tibetan Detachment System and try to discuss its role in the partial melting process that gives rize to the leucogranite in the core of the dome.
This is an interesting topic for the scientific community by the way in my opinion the paper is not suitable for publication in the present form. It presents many issues that should be better explained and clarified. The text is not fluent, english should be strongly revised and very often the geological teminology is not right. In my opinion the conlusions are not well supported by the presented data and the authors need to collect many more structural data to support their conclusion.
Sometimes data and interpretation are mixed together.
The AA do not take in account many published papers , they have to implement the references in the text.
Figures are necessary but some of them need some main modifications
One major problem is that there is , throughout the text, a misunderstanding between “uplift” and “exhumation”. The AA need to speak about exhumation and they have to discuss their data in the frame of all the proposed tectonic models and not only discuss two of them. So they have to implement this part of the discussion and consider a wider range of tectonic models. The discussion should be amplified, if the Authors want to discuss the tectonic models proposed for the exhumation of the metamorphic core of the belt they need to improve it a lot as they missed some main proposed models (i.e. “Channel flow”, “In sequence shearing”).
Another important issue is that it is necessary to document and discuss the evolution of the STDS from contractional to extensional tectonic settings. They refer to paper by Chen et al. 2018 in the area of the Yarlhashampo dome to testify the switch between compression and extension. This is not true as Chen et al. (2018 ) recognized a lower and an upper STDS but both of them show extensional kinematic indicators, so AA must pay attention to the reference and if they have data that support this tectonic switching they have to present them.
For which concerns the Kalopani shear zone (line414), that AA interpreta s a branch of the STDS, it is well established that it is located in the GHS and it is not a branch of the detachment (i.e. between GHS and THS), but it is a top-to-the-South ductile tectonometamorphic discontinuity (sensu Montomoli et al., 2013) responsible for the beginning of the exhumation of the GHS (Carosi et al., 2016)
In addition as the Lhozang fault covers a key role in the proposed tectonic model it is necessary to describe it, its kinematic indicators and related structural elements. This has never been done all along the text
In the “Geological Background” it is mandatory to introduce the geological setting of the study dome.
Introduction
In this paragraph when you describe the different possible interpretations about the origin of the STDS you have also to consider the STDS as a “stretching fault”.
Please add also some more fundamental references about the STDS just to suggest tha most important but there are much more : Searle 1998, Carosi et al., 1998, Waters 2019,Law et al., 2004.
Line 49 Add Wang et al
Line 64 Delete “relevant”
Geological background
The first paragraph of this chapter needs to be completely rephrased. The “extintion” of an oceani s not the right term (Line 71), you can substitute with “closing”. For the main architecture of the study area you have from North to South the southern margin of the Asian Plate, the suture but not the Himalayan orogen as you wrote bit the northern margin of the Indian plate. There isconfusion also in the lines 74-75, please rewrite
Lines 77: Common terminology used by the himalayan scientific community for the main tectonic units building up the belt are:
-Tethyan Himalayan Sequence
- Greater Himalayan Sequence
-Lesser Himalayan Sequence
For the main tectonic discontinuities use the following terminology:
Main Central Thrust delete “fault”
Main Frontal Thrust not Main Front Thrust (Line 83)
Please use the above terminology through all the text .
(Line 85) The active age makes no sense use “age of activity”
Lines 104- 106 Regarding the THS it is not a sub-unit but it is a main tectonic unit building up the belt. The description of the Unit is not clear. At first describe the stratigraphic sequence (see for example Antolin et a 2011 , Dunkl et al 2011) then you can describe the tectonic evolution (see Montomoli et al. 2017, Aikman et al., 2008).
Line110-113: I suggest to delete this sentence as it is not usefull for your paper
Lines 115-116: check that all these faults are represented in the geological map of figure 2 and please use the same names.
Lines 118-119 Delete this sentence. It makes no sense to introduce the local name of the STDS for the western part of the belt. It has many local names across the chain so that it is not necessary to introduce them all.
Lines 124 Add Visonà et al., 2012 (Lithos), Searle 2010.
Line133: This fault THRUSTS some indian….
Line 144 Please give some data regarding the activity of the Rongbu-Gudui fault or refer to literature
Line 155 Substitute “expansion” with “extention”
Lines 163-168 Rewrite this paragraph. Plese have a look to Carosi et al . 2019 Geol. Soc. of London. You need to better describe the GHS. What does it mean that the GHS experienced “magmatic extrusion?”. Parametamorphic rocks, what are they ? Do you mean they are metamorphic rocks from a sedimentary protolith? (“metamorphic rocks and parametamorphic rocks” ??)
Results
Line 175 You never described the “sinistral thrust fault encircling the dome” . You need to introduce the geological setting of the dome. This paragraph is very confusing and I cannot understand which kind of rocks crop out and which is the general architecture of the STDS. In addition figure 3 is not clear. Please refer to paper of Chen et al (2018).
In figure 3B you draw an unconformity. Are you sure this is a primary boundary? Is it not a shear zone?
Line 187: I disagree. Boudins structures not always testify extensional tectonics, they can develop also in a contractional tectonic setting
Lines 275-287 Put this paragraph in the DISCUSSION, here you are presenting your results
Lines 393. This is not uplift but extrusion! You have to discuss all the proposed tectonic models not only these two. See Montomoli et al. 2013 for a review of the tectonic models. See Carosi et al. 2018, 2019, for the “In sequence shearing model” and Kohn 2008 for the “wedge model”.
Figure 1. Some main problems arise from this figure. The AA put the YZSZ inside the THS in central Tibet. This is not the case, if the AA have some data they have to discuss them, anyway the YZSZ is the relict of the Tethyan ocean and it is located between the Indian derived units and the Gandgese batholit. There i salso a Klippen of GHS over the THS in NW part, is i true? Please put some geographic references in the figure
Figure 2 The geological map presents many problems. One main problem regards the legend that should be constructed dividing the different tectonic units (i.e. GHS, THS…) For each unit you should present the different lithostratigraphic unit ordered from the youngest to the oldest. Now it is a completely mess and you mixed all the things.
In addition:
Line 752 I suggest to avoid “eclogite strata”
Line755 What do you mean with “Ophiolite in Creatceous”?
Line758 Spelling “Reverse faut”
Line 759 Are you sure you have gneissic foliation in acid intrusive bodies (see NE of Gonggai)?
Line 760 THS not present in the map
Line 761 YLSP not present in the figure
Yellow field between GT and GCT not present in the legend
Many acronymouses present in the map are not described in the legend (i.e. Pt2-3; K1; J3K1; Tr3…) In the legend everything appearing in the map should be explained
Citation: https://doi.org/10.5194/egusphere-2024-2468-RC2
Viewed
| HTML | XML | Total | BibTeX | EndNote | |
|---|---|---|---|---|---|
| 143 | 43 | 126 | 312 | 3 | 3 |
- HTML: 143
- PDF: 43
- XML: 126
- Total: 312
- BibTeX: 3
- EndNote: 3
Viewed (geographical distribution)
| Country | # | Views | % |
|---|
| Total: | 0 |
| HTML: | 0 |
| PDF: | 0 |
| XML: | 0 |
- 1